Mercer County, IL Climate

Mercer County, IL has a humid continental climate. Summers are warm and humid with temperatures averaging in the mid 80s. Winters are cold with temperatures averaging around 20 degrees. The county receives an average of 37 inches of rainfall per year, with most of that precipitation coming between April and September. Snowfall averages around 21 inches annually, making winter snowfalls a common occurrence. Despite the cold winters, Mercer County is known for its mild summers which offer relief from the chill of winter and provide plenty of opportunity for outdoor activities.

Mercer County, Illinois gets 37 inches of rain, on average, per year. The US average is 38 inches of rain per year.

Mercer County averages 25 inches of snow per year. The US average is 28 inches of snow per year.

On average, there are 201 sunny days per year in Mercer County. The US average is 205 sunny days.

Mercer County gets some kind of precipitation, on average, 98 days per year. Precipitation is rain, snow, sleet, or hail that falls to the ground. In order for precipitation to be counted you have to get at least .01 inches on the ground to measure.

Weather Highlights

Summer High: the July high is around 85 degrees
Winter Low: the January low is 14
Rain: averages 37 inches of rain a year
Snow: averages 25 inches of snow a year

Bestplaces Comfort Index

The annual BestPlaces Comfort Index for Mercer County is 7.0 (10=best), which means it is about average compared to other places in Illinois.

8.7 Summer - 4.8 Winter

September, June and May are the most pleasant months in Mercer County, while January and December are the least comfortable months.

Climate	Mercer, Illinois	United States
	Unlock	38.1 in.
	25.3 in.	Unlock
	Unlock	106.2 days
	201 days	Unlock
	84.9°	85.8°
	Unlock	21.7°
	7	Unlock
	Unlock	4.3
	676 ft.	Unlock

Climate

YOU SHOULD KNOW

Many people confuse weather and climate but they are different. Weather is the conditions of the atmosphere over a short period of time, and climate is how the atmosphere is over long periods of time.

Weather is how the atmosphere is behaving and its effects upon life and human activities. Weather can change from minute-to-minute. Most people think of weather in terms of temperature, humidity, precipitation, cloudiness, brightness, visibility, wind, and atmospheric pressure.

Climate is the description of the long-term pattern of weather in a place. Climate can mean the average weather for a particular region and time period taken over 30 years. Climate is the average of weather over time.

July is the hottest month for Mercer County with an average high temperature of 84.9°, which ranks it as about average compared to other places in Illinois. In Mercer County, there are 5 comfortable months with high temperatures in the range of 70-85°. The most pleasant months of the year for Mercer County are September, June and August.

In Mercer County, there are 15.0 days annually when the high temperature is over 90°, which is cooler than most places in Illinois.

January has the coldest nighttime temperatures for Mercer County with an average of 14.2°. This is colder than most places in Illinois.

In Mercer County, there are 130.0 days annually when the nighttime low temperature falls below freezing, which is colder than most places in Illinois.

In Mercer County, there are 10.4 days annually when the nighttime low temperature falls below zero°, which is colder than most places in Illinois.

The humidity is usually comfortable in Mercer County but some summer months can be unpleasant. July is the most humid month, though humidity is low for most of the year. The most humid months in Mercer County are July, August and June.

June is the wettest month in Mercer County with 4.5 inches of rain, and the driest month is January with 1.4 inches. The wettest season is Autumn with 34% of yearly precipitation and 14% occurs in Spring, which is the driest season. The annual rainfall of 37.2 inches in Mercer County means that it is drier than most places in Illinois.

May is the rainiest month in Mercer County with 10.9 days of rain, and February is the driest month with only 6.4 rainy days. There are 98.1 rainy days annually in Mercer County, which is less rainy than most places in Illinois. The rainiest season is Summer when it rains 29% of the time and the driest is Spring with only a 21% chance of a rainy day.

An annual snowfall of 25.3 inches in Mercer County means that it is snowier than most places in Illinois. January is the snowiest month in Mercer County with 8.1 inches of snow, and 6 months of the year have significant snowfall.

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