Fall Weather in Casper Wyoming, United States

Daily high temperatures decrease by 42°F, from 82°F to 40°F, rarely falling below 25°F or exceeding 90°F.

Daily low temperatures decrease by 29°F, from 51°F to 22°F, rarely falling below 6°F or exceeding 61°F.

For reference, on July 18, the hottest day of the year, temperatures in Casper typically range from 57°F to 88°F, while on December 29, the coldest day of the year, they range from 17°F to 34°F.

The figure below shows you a compact characterization of the hourly average fall temperatures. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Elmadağ, Turkey (6,190 miles away); Hozat, Turkey (6,383 miles); and Bījār, Iran (6,761 miles) are the far-away foreign places with temperatures most similar to Casper (view comparison).

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The fall in Casper experiences very rapidly increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 27% to 48%.

The clearest day of the fall is September 1, with clear, mostly clear, or partly cloudy conditions 73% of the time.

For reference, on March 20, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 53%, while on July 3, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 77%.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In Casper, the chance of a wet day over the course of the fall is decreasing, starting the season at 12% and ending it at 7%.

For reference, the year's highest daily chance of a wet day is 27% on May 22, and its lowest chance is 5% on January 10.

Over the course of the fall in Casper, the chance of a day with only rain decreases from 12% to 2%, the chance of a day with mixed snow and rain remains an essentially constant 1% throughout, and the chance of a day with only snow increases from 0% to 4%.

Rainfall

To show variation within the season and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during the fall in Casper is gradually decreasing, starting the season at 0.6 inches, when it rarely exceeds 1.2 inches or falls below 0.1 inches, and ending the season at 0.1 inches, when it rarely exceeds 0.3 inches.

The highest average 31-day accumulation is 0.8 inches on October 1.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day snowfall during the fall in Casper is increasing, starting the season at 0.1 inches, when it rarely exceeds 0.1 inches or falls below -0.0 inches, and ending the season at 2.2 inches, when it rarely exceeds 4.8 inches or falls below 0.1 inches.

Over the course of the fall in Casper, the length of the day is very rapidly decreasing. From the start to the end of the season, the length of the day decreases by 3 hours, 52 minutes, implying an average daily decrease of 2 minutes, 35 seconds, and weekly decrease of 18 minutes, 2 seconds.

The shortest day of the fall is November 30, with 9 hours, 16 minutes of daylight and the longest day is September 1, with 13 hours, 8 minutes of daylight.

The earliest sunrise of the fall in Casper is 6:30 AM on September 1 and the latest sunrise is 1 hour, 11 minutes later at 7:41 AM on November 2.

The latest sunset is 7:38 PM on September 1 and the earliest sunset is 3 hours, 7 minutes earlier at 4:32 PM on November 30.

Daylight saving time (DST) ends at 1:00 AM on November 3, 2024, shifting sunrise and sunset to be an hour earlier.

For reference, on June 20, the longest day of the year, the Sun rises at 5:26 AM and sets 15 hours, 21 minutes later, at 8:47 PM, while on December 21, the shortest day of the year, it rises at 7:33 AM and sets 9 hours, 1 minute later, at 4:34 PM.

The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.

The figure below presents a compact representation of key lunar data for the fall of 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The chance that a given day will be muggy in Casper is essentially constant during the fall, remaining around 0% throughout.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Casper is very rapidly increasing during the fall, increasing from 9.6 miles per hour to 14.4 miles per hour over the course of the season.

For reference, on January 9, the windiest day of the year, the daily average wind speed is 15.4 miles per hour, while on August 2, the calmest day of the year, the daily average wind speed is 8.6 miles per hour.

The hourly average wind direction in Casper throughout the fall is predominantly from the west, with a peak proportion of 66% on November 27.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season in Casper typically lasts for 4.3 months (134 days), from around May 14 to around September 25, rarely starting before April 25 or after May 31, and rarely ending before September 7 or after October 13.

During the fall in Casper, the chance that a given day is within the growing season is very rapidly decreasing falling from 97% to 0% over the course of the season.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

The average accumulated growing degree days in Casper are rapidly increasing during the fall, increasing by 466°F, from 2,023°F to 2,489°F, over the course of the season.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy in Casper is very rapidly decreasing during the fall, falling by 4.0 kWh, from 6.2 kWh to 2.2 kWh, over the course of the season.

For the purposes of this report, the geographical coordinates of Casper are 42.867 deg latitude, -106.313 deg longitude, and 5,171 ft elevation.

The topography within 2 miles of Casper contains only modest variations in elevation, with a maximum elevation change of 289 feet and an average elevation above sea level of 5,195 feet. Within 10 miles contains only modest variations in elevation (3,153 feet). Within 50 miles contains large variations in elevation (4,823 feet).

The area within 2 miles of Casper is covered by shrubs (76%), artificial surfaces (12%), and grassland (12%), within 10 miles by grassland (48%) and shrubs (41%), and within 50 miles by shrubs (57%) and grassland (39%).