2025 Compare Climate & Weather:
Cheyenne, WY vs O'Fallon, IL

Highlights

On average, there are 202 sunny days per year in O'Fallon. Cheyenne averages 236 sunny days per year. The US average is 205 sunny days.

O'Fallon, Illinois gets 43.1 inches of rain, on average, per year. Cheyenne, Wyoming gets 16.5 inches of rain, on average, per year. The US average is 38.1 inches of rain per year.

O'Fallon averages 11.6 inches of snow per year. Cheyenne averages 58.3 inches of snow per year. The US average is 27.8 inches of snow per year.

Weather Highlights

O'Fallon, Illinois
Summer High: the July high is around 89.2 degrees
Winter Low: the January low is 22
Rain: averages 43.1 inches of rain a year
Snow: averages 11.6 inches of snow a year

Cheyenne, Wyoming
Summer High: the July high is around 84.2 degrees
Winter Low: the January low is 16.4
Rain: averages 16.5 inches of rain a year
Snow: averages 58.3 inches of snow a year

BestPlaces Comfort Index

The annual BestPlaces Comfort Index for O'Fallon is 7.2 (10=best), which means it is one of the most pleasant places in Illinois.

The annual BestPlaces Comfort Index for Cheyenne is 6.8 (10=best), which means it is more comfortable than most places in Wyoming.

Today's Weather - Cheyenne, WY

48°F

Today's Weather - O'Fallon, IL

50°F

Average Monthly High / Low (°F)

Hot, Freezing, Rainy, Snowy Days: Cheyenne / O'Fallon

July is the hottest month for Cheyenne with an average high temperature of 84.2°, which ranks it as cooler than most places in Wyoming. In Cheyenne, there are 4 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for Cheyenne are June, August and September.

July is the hottest month for O'Fallon with an average high temperature of 89.2°, which ranks it as one of the hottest places in Illinois. In O'Fallon, there are 3 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for O'Fallon are May, September and October.

December has the coldest nighttime temperatures for Cheyenne with an average of 15.8°. This is one of the warmest places in Wyoming.

January has the coldest nighttime temperatures for O'Fallon with an average of 22.0°. This is warmer than most places in Illinois.

In Cheyenne, there are 14.0 days annually when the high temperature is over 90°, which is about average compared to other places in Wyoming.

In O'Fallon, there are 39.8 days annually when the high temperature is over 90°, which is one of the hottest places in Illinois.

In Cheyenne, there are 173.4 days annually when the nighttime low temperature falls below freezing, which is warmer than most places in Wyoming.

In O'Fallon, there are 101.4 days annually when the nighttime low temperature falls below freezing, which is warmer than most places in Illinois.

In Cheyenne, there are 8.6 days annually when the nighttime low temperature falls below zero°, which is one of the warmest places in Wyoming.

In O'Fallon, there are 1.6 days annually when the nighttime low temperature falls below zero°, which is one of the warmest places in Illinois.

June is the wettest month in Cheyenne with 2.5 inches of rain, and the driest month is January with 0.3 inches. The wettest season is Autumn with 41% of yearly precipitation and 8% occurs in Spring, which is the driest season. The annual rainfall of 16.5 inches in Cheyenne means that it is wetter than most places in Wyoming.


May is the wettest month in O'Fallon with 4.9 inches of rain, and the driest month is February with 2.4 inches. The wettest season is Summer with 28% of yearly precipitation and 18% occurs in Spring, which is the driest season. The annual rainfall of 43.1 inches in O'Fallon means that it is wetter than most places in Illinois.

May is the rainiest month in Cheyenne with 11.2 days of rain, and January is the driest month with only 4.2 rainy days. There are 91.9 rainy days annually in Cheyenne, which is rainier than most places in Wyoming. The rainiest season is Autumn when it rains 33% of the time and the driest is Spring with only a 16% chance of a rainy day.

May is the rainiest month in O'Fallon with 10.9 days of rain, and February is the driest month with only 6.6 rainy days. There are 96.4 rainy days annually in O'Fallon, which is one of the least rainy places in Illinois. The rainiest season is Summer when it rains 30% of the time and the driest is Spring with only a 22% chance of a rainy day.

An annual snowfall of 58.3 inches in Cheyenne means that it is snowier than most places in Wyoming.

An annual snowfall of 11.6 inches in O'Fallon means that it is less snowy than most places in Illinois.

March is the snowiest month in Cheyenne with 11.0 inches of snow, and 9 months of the year have significant snowfall.

January is the snowiest month in O'Fallon with 3.8 inches of snow, and 4 months of the year have significant snowfall.