A Climatic Handbook For Glacier National Park-with Data .

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This file was created by scanning the printed publication.Errors identified by the software have been corrected;however, some errors may remain.United StatesDepartment ofAgricultureForest ServiceIntermountainResearch StationGeneral TechnicalReport INT-204July 1986A Climatic Handbookfor Glacier NationalPark with Data forWaterton LakesNational ParkArnold I. Finklin

RESEARCH SUMMARYTHE AUTHORThis publication presents climatic details for theGlacier National Park-Waterton Lakes National Parkarea in northwestern Montana-Alberta; data and analysis mainly cover the Montana area. The content,including numerous tables and graphs, is intended toprovide information to aid fire management planningand other wildland resource activities. Data are summarized and analyzed from year-round climatologicalstations, fire-weather stations, and additional sources.Weather and climatic elements are examined individually. In addition, combinations of temperature, relativehumidity, and windspeed data are included for the fireseason.The data show some of the elevational and othertopographic effects identified with mountainous areas.Despite large differences in average values, the dataalso show a general similarity-within the parkboundary-in the normal annual regimes of the climatic elements; an exception occurs with windspeed.For example, November, December, and January arethe heaviest precipitation months within most ofGlacier Park, even though normal annual precipitationranges from about 23 inches (585 mm) to 100 inches(2 500 mm) or more. July and August are normally thedriest months of the year. The pattern differs-withrelatively light winter (and annual) precipitation-onthe plains immediately east.High interstation correlations are found for afternoon temperatures; correlations are moderately highfor precipitation amounts. A persistence tendency isindicated between late spring (May-June) and summer(July-August) maximum temperatures and precipitation,relative to normal, but not between the individualmonthly values. Climatic trends or fluctuations duringthis century, examined by running means, show recentJuly-August 11-year rainfall amounts well above normal, while September-October was abnormally dry.Fire-weather statistics of afternoon temperature andrelative humidity, if based on these recent summers,give a cooler and more moist picture than that of thelonger term. Our climatic findings do not supportsome published explanations for the historicallygreater fire activity on the west side of Glacier Park.The east side, overall, has about as much precipitationaccumulation and thunderstorm occurrence as thewest side.ARNOLD I. FINKLIN is a meteorologist at the Intermountain Fire Sciences Laboratory, Missoula, MT,specializing in climatology. He received a master'sdegree in atmospheric science from Colorado StateUniversity before joining the laboratory in 1967.CONTENTSPageIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Description of the Area . . . . . . . . . . . . . . . . . . . . . . . . . 1Physical Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Forests; Fires . : 4Stations; Data; Methods . . . . . . . . . . . . . . . . . . . . . . . . 5Averages; "Normals" . . . . . . . . . . . . . . . . . . . . . . . . . 8Condensed Summary of the Climate . . . . . . . . . . . . . . 8Summary by Seasons . . . . . . . . . . . . . . . . . . . . . . . . . 8Summary by Individual Elements . 10Details of the Climate . 11Climatic Controls; Broad Weather Patterns . 11Precipitation . 12Temperature . 22Relative Humidity . 31Wind . 37Sunshine; Solar Radiation . 41Evapotranspiration . 43Runoff . 44Weather Correlations Between Locations . 46Persistence of Weather . 49Climatic Trends . . . . . . . . . . . . . . . . 49Summary . 51References . 52Appendix: Tables 17-36 . 56The use of trade, firm, or corporation names in thispublication is for the information and convenience ofthe reader. Such use does not constitute an officialendorsement or approval by the U.S. Department ofAgriculture of any product or service to the exclusionof others that may be suitable.July 1986Intermountain Research Station324 25th StreetOgden, UT 84401

A Climatic Handbook forGlacier National Park-withData for Waterton LakesNational ParkArnold I. FinklinINTRODUCTIONTo its visitors, Glacier National Park, MT, offers acloseness to the marvels of nature. Although its alpineterrain features give the park its special character, theflora and fauna are also major aspects of Glacier. Hereand in other lands under its administration, the U.S.Department of the Interior, National Park Service, isgiven the mission of preserving the area's natural state(in addition to providing for public use). In recent years,Park Service policy (Kilgore 1976) has come to recognizethe historic, natural role of fire in shaping and maintaining the diversified wildland ecosystems. Fire management now seeks to allow some natural, lightning-causedfires to burn (within prescribed limits) and also to utilizeplanned ignitions-in contrast to the earlier effortstoward total fire suppression. Implementation of thisnew policy has been slow in Glacier Park, because ofnecessary concerns about public acceptance and safety,and lack of specific information to guide decisions.Interest has thus far concentrated on the more fire-pronewest side of the park. A prescribed burn was successfully conducted near Polebridge in 1981; a second one in1983.Data needed for fire management are being obtainedby research concerning fire history (Barrett 1983), firesusceptible terrain (Key 1984), and prescribed burning.Cooperating with Glacier Park personnel in these studieshas been the U.S. Department of Agriculture, ForestService, at its Intermountain Research Station, Intermountain Fire Sciences Laboratory, Missoula, MTtogether with Systems for Environmental Management,Missoula. Data used for planning also include those ofweather and climate-for example, in establishing seasonal limits for prescribed burning. Climatic data can, inaddition, establish a baseline for use in evaluating fireeffects. These effects, such as postfire vegetativeresponse, may be strongly influenced by the normal orabnormal extent of weather conditions in the ensuingmonths and years.This publication, termed a handbook, is intended to fillsome of the climatic data void. Though prepared largelyas a reference for fire managers, the handbook includesdata for other management and research activitieswithin the park and adjoining areas. Thus, the contentmay also have applications relating to forest ecology,wildlife, hydrology, recreation, and to rangelands justeast of the park on the Blackfeet Indian Reservation.The data coverage includes W aterton Lakes NationalPark, AB, part of Waterton-Glacier International PeacePark. The main coverage available, however, is forGlacier Park and adjacent Montana.A brief climatic description of Glacier National Park.aimed toward the general public, was prepared byDightman (1967a). The climate of Waterton LakesNational Park has been described by Poliquin (1973). Inneighboring Rocky Mountain areas, Dirks and Martner(1982) present climatic details for Yellowstone andGrand Teton National Parks; they also refer to moreextensive University of Wyoming project reports. Aclimatic report by J anz and Storr (1977) covers Y oho,Kootenay, Banff, and Jasper National Parks in BritishColumbia and Alberta. Local topographic and site effectson summer climate in a forest area southeast of Banffare described by MacHattie (1966, 1968, 1970).The present handbook includes climatic details for thefire season, to 10-day resolution, together with the yearround pattern. In addition to graphs and tables appearing within the text, detailed summary tables and datalistings are given in an appendix. The scope does notcover related or derived factors such as fuel moistureand fire-danger indexes. Because our objective is to present climatic information, detailed physical or technicalexplanations have been left to references. Sources forelementary background in weather and climate includeSchroeder anc Buck (1970); Critchfield (1974); Landsberg(1958); Reifsnyder (1980).In discussing the climatic elements over the course ofa year, this report will mostly follow the format of treating the elements individually. A description combiningthe elements by seasons is, however, included in the section, ''Condensed Summary of the Climate.''DESCRIPTION OF THE AREAPhysical FeaturesThe location of Glacier and W aterton Lakes NationalParks is shown in figure 1. Covering a total area of1,143,000 acres (462 500 ha) near and astride theContinental Divide and the Canadian-United States border (49th parallel of latitude), this land will also bereferred to as Waterton-Glacier-the name of the International Peace Park established in 1932. Glacier, comprising 1,013,000 acres (410 000 ha), became a NationalPark in 1910; Waterton Lakes, with 130,000 acres(52 500 ha), began its preservation as a "Forest Park" in1895 (Buchholtz 1974).

Calgary SuffieldBRITISH COLUMBIAincher Creek Castle garCranbrook Old Glory Mtn. LethbridgeSASKATCHEWANALBERTAWASHINGTONMONTANA Cut Bank Spokane Mullan PassGreat Falla IDAHOHelenaOREGON02660100 Mlus owFigure 1.-Location of Glacier and Waterton Lakes National Parks (Waterton-GiacierInternational Peace Park) (stippled area), together with surrounding weather stationsmentioned in text.The basic geological history of this area starts withthe Precambrian layers of limestones, mudstones, andsandstones-formed from sediments deposited in a seafilled trough (called the Belt Sea) and intruded bymagma. Subsequent events include: the uplift andfolding of these layers during the mountain-buildingperiod that began about 75 million years ago; a fractureinitiating the Lewis Overthrust Fault, on which a hugeslab of rock ultimately slid about 40 miles (65 km) eastward and covered rock 1 billion years younger; and theprocesses of erosion by water and (within the past2 million years) by glaciers, shaping the terrain to itspresent appearance. (See Dyson 1966, 1967; Alt andHyndman 1973.)The main drainage features and elevations of thehighest peaks are shown in figure 2. No attempt is madeto depict the complex and steep terrain contourpattern-available from U.S. Department of the Interior,Geological Survey, topographic maps. Elevations withinGlacier Park range from about 3,110 ft (948 m) a.s.l.(above sea level) at the Middle Fork-North ForkFlathead River confluence to 10,466 ft (3 190m) atopMount Cleveland (fig. 3). Within Waterton Lakes Park,elevations range from just under 4,200 ft (1 280m) to9,646 ft (2 940 m) atop Mount Blakiston. The ContinentalDivide trends generally from northwest to southeast. Itis formed mostly by the Lewis Range, which runs thelength of the park from east of W aterton Lake, but alsoby the smaller Livingston Range (farther west) in thenorthern portion. W aterton Park lies entirely on the eastside of the Divide, while 60 percent of the Glacier Parkland area is on the west side. Waterton-Glacier contributes to three major drainage systems, and a triple divideexists south of St. Mary Lake-separating flows intoHudson Bay, the Gulf of Mexico, and the Pacific Ocean.The present glaciers, numbering about 50 in GlacierPark, are not remnants from the great ice ages (the lastone ending about 10,000 years ago), but instead arebelieved to have originated about 4,000 years agofollowing an intervening warm period. These lesserglaciers (and others since melted) apparently reachedtheir maximum extent in the 1850's (Carrara and

-----,, ,- . CARDSTON3785CALDWELL Q4300MOUNTAIN VIEW4323,-,.LEE CREEK BASIN4575' }CA: :8YALBERT A--------- -- --- --------MONTANABABB 8NE4300KALISPELLP 298501 21020 Ml Regular climatological station, year-round temp. and precip. Other year-round station (for research, etc.), data mainly from recording charts. Fire-weather or seasonal station.f2lStorage precip. gage, annual or semi'-annual readings.0Snow survey course.0Precip. only.t lSIoPrecip. only.Temp. only.0Precip. only."SNOTEL" precip.Figure 2.-Map of Waterton-Giacier Park area, showing drainage features (streamsarid Jakes) and locations of stations providing data used in this report; symbols indicate type of station. Park boundary is shown by heavy line, Continental Divide bydashed line. Station elevations, and those of some high peaks, are given in feet. RSdenotes Ranger Station; LO, Lookout; GG, Grinnell Glacier (gauges No. 1 and 2); GL,Grinnei1 Lake (elev., 4,925 ft). Two-letter abbreviations of snow courses are identifiedin table 27. Superscript F denotes formerly existing station (or station network); FP,former climatological station replaced by "Fischer-Porter" precipitation gauge.

(Populus tremuloides) groves, limber pine (Pinus flexilis),and Douglas-fir. This eastern area is well grazed by wildlife such as elk and deer and (beyond the park) bylivestock.The highest elevation forests, below the alpinemeadows and Krummholz vegetation, are dominated bysubalpine fir (Abies lasiocarpa), Engelmann spruce (Piceaengelmannii), and whitebark pine (Pinus albicaulis).Fire has long had an important role in shaping andmaintaining the forest ecosystems and their attendantdiversity. In what is now Glacier Park, natural(lightning-caused) fires appear to have been much morefrequent in the western portion than on the east side. Asimple, partial explanation is that about two-thirds ofthe forested area is located on the west side. From thetime of Glacier's establishment in 1910 through the year1968, 90 percent of 525 reported lightning-caused firesoccurred west of the Continental Divide, with close to 50percent in the Lake McDonald subdistrict (O'Brien1969). In the northwestern part of Glacier, a threecentury fire history by Barrett (1983) revealed frequentand sometimes extensive underburns followed by occasional stand-replacing fires. The replacement-type firesappear to be more typical and significant, however, forthe overall park area (personal communication from CarlH. Key, geographer, National Park Service). As much as90 percent of Barrett's 60,000-acre (24 000-ha) studyarea has underburned within the past 56 to 95 yearsbut little since 1930, in an era of strong fire suppression.O'Brien (1969) found that 98 percent of Glacier's1910-68 fires occurred between June 19 and September19, with 30 percent in July and 51 percent in August.Nine percent (48) of the fires reached Class C size (10acres [4 ha]) or larger, with 40 percent of these in Julyand 44 percent in August. Further analysis showed that95 percent of the fires occurred at elevations below7,100 ft (2 165m) and about two-thirds on southernaspects. In· a west-side area examined by Key (1984),lightning-ignition frequencies during 1910-82 indicated agreater susceptibility along certain ridge systems, at elevations below 4,000 ft (1 220m), and on westerly andsouthwesterly aspects.Memorable fires in Glacier Park include those in 1910,1926, 1929, 1936, and 1967 (Robinson 1960; Habeck1970). In the latter two years, fire swept eastward overthe Continental Divide. The Heavens Peak Fire inAugust 1936, roaring down the Many Glacier Valley,completely or partially stripped about 7,500 acres(2 300 ha) (fig. 4). It burned the ranger station and othe1buildings but spared the hotel. A year earlier, a largefire affecting both Glacier and Waterton was stoppedwithin about 1.5 miles (2.4 km) of the Waterton Parktownsite. The new fire management policy of theNational Park Service (Kilgore 1976) does, of course,continue suppression in such developed areas. Two large,wind-driven fires in late August 1984, on or adjoiningthe southwestern and eastern edges of Glacier Park,ended a 17 -year period of relative quiet.Figure 3.-Mount Cleveland (capped bycloud), highest peak in Waterton-GiacierPark, at 10,466 ft (3 191 m); viewed towardsoutheast from Waterton Lake, September1954.McGimsey 1981). The drastic melting and retreat sincethat time, particularly during the 1920's and 1930's, isshown by the above authors and by Dyson (1966) andJohnson (1980). The largest glaciers, Grinnell andSperry, now cover less than 300 acres (120 ha) each.Relation of this melting to climatic change or fluctuationwas examined by Dightman (1952, 1956, 1967b).Although the rate of recession slowed considerably by1950, and an advance of Grinnell Glacier was measuredin 1951, the overall retreat continues.Forests; FiresForests cover two-thirds of Glacier Park's land area(Kessell 1979). They occur mostly below an elevation of7,000 ft (2 135 m)-limited by steep, rocky terrain as wellas the climatic timberline. A contrast between forests onopposite sides of the Continental Divide has been notedby Habeck (1970), Robinson (1972), and Kessell (1979).The idealized elevational distribution of tree species (andforest community types) is complicated by local sitedifferences and by the varying stages of succession following past fires.Lodgepole pine (Pinus contorta) is widespread at lowerand intermediate elevations. There is also much westernlarch (Larix occidentalis) and some western white pine(Pinus monticola) on the west side of Glacier Park. Climax species there include western redcedar (Thujaplicata) and western hemlock (Tsuga heterophylla), foundin the Lake McDonald vicinity-their easternmost extentin North America (Habeck 1968). Spruce (Piceaengelmannii X P. glauca hybrid), Douglas-fir(Pseudotsuga menziesii), and subalpine fir (Abieslasiocarpa) are climax species in other west-side areas.Ponderosa pine (Pinus ponderosa), apparently seral,occurs near Polebridge. Near the eastern park boundary,the lodgepole pine joins a mixture of prairie, aspen4

Figure 4.-Many Glacier area, 1954, 18 years after the Heavens Peak Fire. (A) Alongtrail to Iceberg Lake; Mount Wilbur and Ptarmigan Wall in background. (B) At campground, lodgepole pine regenerating, looking west toward Mount Wilbur andSwiftcurrent Pass (topped by cloud bank at left). The fire swept over this pass fromwest side of Continental Divide.1979, with a few shifts in instrument location and manychanges in observer. Precipitation measurements continue at Summit from a Fischer-Porter (punched-tape)recording gauge, which also transmits the data via satel·lite. Further station-history details, for these and otherplaces, are given by U.S. Weather Bureau (1956) andDightman (1967a).The detailed summary tables were in part obtainedthrough a data tape furnished by Dr. Joseph M. Caprio,State Climatologist at Bozeman, MT, and computer programs by Bradshaw (Bradshaw and Fischer 1984). Thetape contained daily observations for the years 1949through 1978. Additional data were tabulated frommonthly and annual issues of "Climatological Data"State summaries for Montana and from U.S. WeatherBureau (1937, 1955, 1965); also from records furnishedby the N atiorial Climatic Center, Asheville, NC. Tabulated data included those for the long-term climatic stations at Babb 6NE (6 miles NE) and Browning, bothlocated east of Glacier Park in prairie or rangeland; thestation at Browning was discontinued in 1980 (butreplaced by a Fischer-Porter gauge).STATIONS; DATA; METHODSLocations and elevations of stations utilized in thisreport are included in figures 1 and 2. The stations infigure 1 are (or were) primary daily reporting stations,located mostly at airports. Those shown in figure 2, inMontana, are of two main types: (i) the year-roundclimatological substations ("cooperative" stations) of theNational Weather Service (formerly U.S. WeatherBureau) and (2) the seasonal fire-weather (or fire-dangerrating) stations of the Forest Service and National ParkService.Detailed temperature and precipitation summarytables are presented for three of the cooperativestations-Polebridge, Summit, and West Glacier (fig. 5),all located on the perimeter of Glacier Park. Data fromWest Glacier have been observed near the present Parkheadquarters since 1918; a continuous record dates from1926. The Polebridge data, mostly complete from 194 7to the present, are from the mercantile-post office location except for a 2-year period at the ranger station,1.3 miles (2.1 km) to the north-northeast. Earlier, incomplete records from the ranger station go back to 1933.At Summit, observations were taken from 1935 to early5

Figure 5. -Climatological stations on perimeter of Glacier Park; 1982 photographsexcept as noted. (A) West Glacier, near Park Headquarters. Thermometer shelter incenter, precipitation gauges at left (Fischer-Porter recording type, with windshield)and right ("stick" type); snow-depth marker also visible. (B) Polebridge; thermometershelter behind building housing mercantile and post office, precipitation gauge inopen area to right of photo. (C) Summit, original station location near railroad; thermometer shelter in mid-background; 1947 photo from Corps of Engineers (1952b). (D)Present station near Summit (Marias Pass), Fischer-Porter gauge only; antenna to.left of gauge for transmission of data via satellite. Thermometer shelter was locatedon the wooden platform during 1967-73.Data for the fire-weather stations were accessed fromtapes at the National Fire-Weather Data Library, FortCollins, CO (Furman and Brink 1975), and from originalforms filed through 1970 at the Intermountain FireSciences Laboratory. Summary tables again wereobtained through the computer programs of Bradshawand Fischer (1984). A few of the stations are pictured infigure 6. The fire-weather data in this report are basedprimarily on observations near 4 p.m. (1600) m.s.t., thestandard prior to 197 4; observations have been at 1 p.m.(1300) since then. As shown later, the change-made inaccordance with new national standards-has resulted insome noncomparability with previous data.As noted· in figure 2, data were also obtained from stations in research areas. Locations include the formerUpper Columbia Snow Laboratory, near Summit (orMarias Pass), where hydrometeorological data wereobserved during 1946-51 (Corps of Engineers 1949,1952a,b,c,d); also the Coram Experimental Forest, southof West Glacier (Hungerford and Schlieter 1984). Otherdata include year-round records at St. Mary RangerStation furnished by Jerry Ryder, Subdistrict Ranger,Glacier National Park.Climatic averages for locations in Canada are, in part,from Atmospheric Environment Service (1982a,b,c).Special W aterton Park-area data were provided byDavid R. Graham, River Forecast Center, AlbertaEnvironment, and Henry Turchanski, AtmosphericEnvironment Service, Environment Canada-both atEdmonton, and the report by Poliquin (1973). A copy ofthat report and other, first-hand information were furnished by Robert A. Watt, Warden Service, ParksCanada, W aterton Park.6

Figure 6.-Fire-weather or seasonal stations, Glacier National Park area; 1982 photographs except as noted. (A) West Glacier; site, more open, is about one-half milenorthwest of year-round climatological station (fig. 5). Air-sampling equipmentlocated on wooden platform. (B) Polebridge, at Ranger Station. Wind is, at present,measured with hand-held meter. (C) St. Mary; site one-fourth mile northwest ofRanger Station (and present year-round station). Napi Point and part of 1984 firearea in distance. (D) Hungry Horse, at Ranger Station (1984 photo). (E) Many Glacier,at Ranger Station; temperature and precipitation measurements only.7

Data from \fontana snow-survey courses. giving snowpack depth and water content. are from the Soil Conservation Service (SCSH19i5l and from monthly issues ofthat agency's "\\"ater Supply Outlook. . The SCS officeat Bozeman. \IT. through Phillip E. Farnes. provided"SXOTEL . (snow telemetry) data: these include cumulative water-year (October-September) precipitation. as atthe station in figure i. Streamflow. or runoff. data wereobtained from bulletins of the U.S. Department of theInterior. Geological Survey (USGS). and from the USGSdistrict office in Helena. T. Additional data sourcesare identified later within the text.As already noted. this time was changed by 3 hours in19i 4. Fire-weather averages are presented for 1951-80 inseveral graphs. adjusting the more recent data to theprevious 1600 m.s.t. observation time. which betterrepresented the extreme afternoon conditions.Likewise. for comparability among locations. averagesat stations with short periods of record have beenadjusted to the 30-year period. The calculations. involving adjacent long-term stations. employ the "differencemethod·· for temperature and relative humidity: the"ratio method . for precipitation (Oliver 19i3: Finklin1983al.Even with 30 years of data. 10-day averages are apt toexhibit irregularity. largely accidental. Thus. smoothingis employed in some of the graphs-mainly a running1-4-1 weighting factor applied to successive 10-dayvalues.Averages have been further adjusted in the case ofmaximum and minimum temperatures-to a 24-hourperiod representing the actual calendar day. midnight tomidnight. This is the reference period used at the primary (airport) stations of the ational \\r eather Service.The observed average maximums at cooperative and fireweather stations. with data for a 24-hour period endingnear 1600 or 1700. are as much as 2 oF (1 C) higherthan those for the calendar day (Rumbaugh 1934:Finklin 1983a): see table 17 (appendix).Another estimate or adjustment was involved inpresenting averages of temperatures for a fixed higherelevation. or 6.000-ft (1 830-m) slope location. as in figure22 in the "Temperature . section. In this case. thealready-obtained normals from two short-record parkarea stations near this elevation were adjusted for compatibility with normals computed for the former stationsat Mullan Pass. ID. Old Glory Mountain. BC (fig. 1).and Bangtail Ridge (near Bozeman. MT). and also forlookout stations. This took into account elevational andhorizontal temperature gradients (shown in abovesection).Figure 7. -SNOTEL (snow telemetry) stationat Many Glacier; site between RangerStation and Swiftcurrent Lake. Snow courseis along fence; snow pillow, precipitationgauge with windshield, temperature sensor(inside vane-type shield), and antenna mastare within enclosure.The fire-weather and various climatic data werechecked for errors and missing values. Using availablebackup sources and comparisons with adjacent stations,highly suspect daily and monthly values were corrected,replaced with estimates, or discarded. Estimates weremade where possible for the missing values, which couldbe important in some cases (Finklin 1983a). Precipitationand snowfall measurements that occasionally covered aperiod of 2 or more days were apportioned to individualdays. A backup source that aided in some of this editingwas the monthly publication, "Hourly PrecipitationData," summary for Montana. That publication alsoprovided data for continuing part of the record atSummit, referred to earlier.CONDENSED SUMMARY OF THECLIMATESummary by SeasonsThe seasons in the Waterton-Glacier area do not easilyfollow the widely used or standard 3-month divisions.Seasons adopted by the National Climatic Center in theUnited States are based on the 3 successive months thatordinarily have the highest and lowest average temperatures during the year. Thus, while June, July, andAugust comprise the standard summer season, June ismore of a spring month in Waterton-Glacier-withweather more similar to that in May than to that inJuly-August. December, January, and February comprise the standard winter season. However. from considerations of below-freezing average temperatures andsnowfall, winter in Waterton-Glacier may properly alsoinclude much of November and March. This leaves April.May, and June as the suggested spring season andSeptember-October representing autumn.Averages; ''Normals''Climatic averages in this handbook include those for astandard 30-year "normal" period (currently 1951-80), asadopted by international convention; the normal valuesare revised every 10 years. The 30-year length tends tobalance out short-term variations, though a longer periodis desirable for precipitation (World MeteorologicalOrganization 1967). A 20-year data sample, however, hasbeen used in fire-weather summary tables, governed byavailability of data at an unchanged observation time.8

tions. Daily maximums in June average near 70 F(21 C) at lower elevations. Corresponding afternoon relative humidity averages near 45 percent. Last "killing"frost or 28 F (- 2 C) minimum temperature occursaround mid-May to mid-June at lower valley locations.Average wind speeds on the east side of the park show aseasonal decrease from their winter maximum. In thewestern valleys, average speeds are at their highest inspring, though still a few miles per hour lower than onthe east side. Although spring days are often cloudy, thepercentage of maximum possible sunshine durationincreases to about 50 to 60 percent.Summer.-A large change in average conditions occursin July. The short (2-month) summer, the main fire season, is usually a time of minimum cloudiness andprecipitation within Waterton-Glacier. July precipitationtotals average about 1.5 inches (38 mm) near the parkedges; 2.5 to 3.0 inches (65 to 75 mm) over the parkinterior near the Continental Divide. August has slightlyhigher averages. In individual years, summer monthlytotals at perimeter locations such as West Glacier, MT,may be near zero or as high as 4 to 5 inches (100 to125 mm). Snowfall, limited to higher terrain and occasional years, has reached at least 9 inc

Park, AB, part of Waterton-Glacier International Peace Park. The main coverage available, however, is for Glacier Park and adjacent Montana. A brief climatic description of Glacier National Park. aimed toward the general public, was prepared by Dightman (1967a). The climate of Waterton Lakes National Park has been described by Poliquin (1973 .

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