30-year climate normals

Shelby County Climate and Weather Averages

Hottest month — July

86.0°

average daily high. The coldest month is January, averaging a low of 19.2°F.

Shelby County gets 41.44" 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.

Month	Avg high	Avg low	Precip
January	35.9°	19.2°	2.60"
February	41.1°	22.9°	2.07"
March	51.9°	32.1°	2.71"
April	64.0°	43.1°	4.33"
May	73.7°	54.3°	4.65"
June	82.5°	63.4°	4.68"
July	86.0°	66.6°	4.06"
August	84.9°	64.6°	3.41"
September	79.6°	56.6°	3.06"
October	67.1°	44.8°	3.57"
November	52.3°	33.5°	3.71"
December	40.6°	24.7°	2.59"

Rainfall by month

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

January 2.60"

February 2.07"

March 2.71"

April 4.33"

May 4.65"

June 4.68"

July 4.06"

August 3.41"

September 3.06"

October 3.57"

November 3.71"

December 2.59"

Annual total 41.44"

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 1,186

Heating degree days How much heating the climate demands 5,321

Approximate annual cooling cost At 23.85¢/kWh, Illinois average $283

Approximate annual electric heating cost Lower where heating is gas rather than electric $444

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 Shelby County, where electricity is one line of eight.

Common questions

What is the weather like in Shelby County?

Shelby County averages a high of 86.0°F in July and a low of 19.2°F in January. Annual precipitation is 41.44 inches, with essentially no snow.

When is the rainy season in Shelby 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 Shelby County?

The average daily high in July, the hottest month, is 86.0°F. That drives 1,186 cooling degree days a year, which is what your air conditioning has to work against.

Does it snow in Shelby County?

Effectively no. Measurable snowfall is rare in Shelby County.

Sources

Temperature, precipitation and snowfall normals — NOAA National Centers for Environmental Information, 1991–2020 Monthly Climate Normals, station SHELBYVILLE DAM, IL US (USC00117876), 2.1 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.