Wyoming Annual Temperatures and Extremes

 

Wyoming's Temperature Records

Hottest temperature ever recorded: 116 F, Basin, north-central Wyoming, 8/8/1983 Coldest temperature ever recorded: -66 F, Riverside, southern Wyoming, 2/9/1933 Hottest location ranked by highest average annual temperature: Lingle, southeastern Wyoming, 50.0 F Coldest location ranked by lowest average annual temperature: Lake Yellowstone, northwestern Wyoming, 32.0 F Wyoming's record for most consecutive days with the high temperature equal to or exceeding 90 degrees was set in July through August 1964 with 41 days at Basin, Wyoming. The record for most consecutive days with the low temperature equal to or below 32 degrees was set in October 1967 through July 1968 at Kendall, New Mexico with 277 days.

Due to its elevation, Wyoming has a relatively cool climate. Above the 6,000 feet level, temperatures rarely exceeds 100° F. The warmest parts of the State are the lower portions of the Big Horn Basin, the lower elevations of the central and northeast portions and along the eastern border. The highest recorded temperature is 115° F on August 8, 1983, at Basin in the Big Horn Basin. The average maximum temperature at Basin in July is 92° F. For most of the State, mean maximum temperatures in July range between 85 and 95. With increasing elevation, average values drop rapidly (3.0 to 5.5° F per 1,000 feet). A few places in the mountains at about the 9,000 foot level have average maximums in July close to 70. Summer nights are almost invariably cool, even though daytime readings may be quite high at times. For most places away from the mountains, the mean minimum temperature in July ranges from 50 to 60° F. Of course, the mountains and high valleys are much cooler with average lows in the middle of the summer in the 30s and 40s with occasional drops below freezing.

In the wintertime, it is characteristic to have rapid and frequent changes between mild and cold spells. Usually there are less than 10 cold waves during a winter and frequently less than half that number for most of the State. The majority of cold waves move southward on the east side of the Divide. Sometimes only the northeast part of the State is affected by the cold air as it slides eastward over the plains. Many of the cold waves are not accompanied by enough snow to cause severe conditions. In January, the coldest month generally, minimum temperatures range mostly from five to 10° F. In the western valleys mean values go down to about -5. The record low for the State is -66° F observed February 9, 1933, at Yellowstone Park. During warm spells in the winter, nighttime temperatures frequently remain above freezing. Chinooks, warm downslope winds, are common along the eastern slopes.

Numerous valleys provide ideal pockets for the collection of cold air drainage at night. Protecting mountain ranges prevent the wind from stirring the air, and the colder, heavier air settles into the valleys often sending readings well below zero. It is common to have temperatures in the valleys considerably lower than on the nearby mountain side. Big Piney in the Green River Valley is such a location. Mean January temperatures in the Big Horn Basin show the variation between readings in the lower part of the valley and those higher up. At Worland and Basin in the lower portion of the Big Horn Basin, not far from the 4,000 foot level, the mean minimum temperature for January is 2° F, while Cody, close to 5,000 feet on the west side of the valley has a mean January minimum of 15. January has occasional mild periods when maximum readings will reach the 50s; however, winters are usually long and cold.

For most of Wyoming, sunshine ranges from 60 percent of the possible amount during the winter to about 75 percent during the summer (ranks 9th in the US with an annual average of 64 percent). Mountain areas receive less, and in the wintertime the estimated amount over the northwestern mountains is about 45 percent. In the summertime when sunshine is greatest, not only in time but also intensity, it is characteristic for the mornings to be mostly clear. Cumulus clouds develop nearly every day and frequently blot out the sun for a portion of the afternoons. The altitude has less atmosphere for the sun’s rays to penetrate and because of the very small amount of fog, haze and smoke, the intensity of sunshine in unusually high.

Wyoming precipitation averages and extremes, precipitation and temperature data for all U.S. states and Top 10 U.S. climate extremes
Data source: National Climatic Data Center