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United States › Illinois › Monroe County › Climate Station CAHOKIA ST LOUIS AP, IL US Distance 20.3 mi Normals 1991–2020

30-year climate normals

Monroe County Climate and Weather Averages

Hottest month — July

89.0°

average daily high. The coldest month is January, averaging a low of 24.1°F.

Monroe County gets 40.84" of precipitation a year, and 33% of it falls in Apr, May, Jun.

Temperature through the year

Each bar spans the average daily low to the average daily high for that month.

40° 60° 80° JanFebMarAprMayJunJulAugSepOctNovDec
MonthAvg highAvg low Precip
January 40.2° 24.1° 2.46"
February 45.6° 27.6° 1.96"
March 56.3° 36.0° 3.27"
April 67.5° 45.5° 4.48"
May 76.7° 56.5° 4.84"
June 85.7° 64.7° 4.36"
July 89.0° 68.8° 3.70"
August 87.8° 66.1° 3.68"
September 80.7° 57.1° 3.36"
October 69.4° 46.1° 3.07"
November 55.3° 35.9° 3.34"
December 44.3° 28.6° 2.32"

Rainfall by month

Precipitation is spread fairly evenly through the year here, with 33% falling in the wettest three months (Apr, May, Jun).

January 2.46"
February 1.96"
March 3.27"
April 4.48"
May 4.84"
June 4.36"
July 3.70"
August 3.68"
September 3.36"
October 3.07"
November 3.34"
December 2.32"
Annual total 40.84"

What this climate costs you

Degree days measure how hard a building has to work to stay comfortable. They are the reason two identical houses have very different power bills, and they are the link between the weather here and what you pay every month.

Cooling degree days How much air conditioning the climate demands 1,476
Heating degree days How much heating the climate demands 4,547
Approximate annual cooling cost At 23.85¢/kWh, Illinois average $352
Approximate annual electric heating cost Lower where heating is gas rather than electric $380

These are rough planning figures from degree days and the state electricity price, not a bill estimate. House size, insulation and fuel type move them a lot. See the full cost of owning a home in Monroe County, where electricity is one line of eight.

Common questions

What is the weather like in Monroe County?

Monroe County averages a high of 89.0°F in July and a low of 24.1°F in January. Annual precipitation is 40.84 inches, with essentially no snow.

When is the rainy season in Monroe County?

The wettest stretch is Apr, May, Jun, which accounts for 33% of the year's precipitation. Precipitation is relatively evenly distributed across the year.

How hot does it get in Monroe County?

The average daily high in July, the hottest month, is 89.0°F. That drives 1,476 cooling degree days a year, which is what your air conditioning has to work against.

Does it snow in Monroe County?

Effectively no. Measurable snowfall is rare in Monroe County.

Sources

  • Temperature, precipitation and snowfall normals — NOAA National Centers for Environmental Information, 1991–2020 Monthly Climate Normals, station CAHOKIA ST LOUIS AP, IL US (USW00003960), 20.3 miles from the county centroid.
  • Heating and cooling degree days — NOAA, same station and period.
  • Electricity price — US Energy Information Administration, Electric Power Monthly Table 5.6.A, Illinois residential average.
  • Wet-season share is the wettest three consecutive months as a percentage of annual precipitation, calculated from the monthly normals.