30-year climate normals

Marion County Climate and Weather Averages

Hottest month — July

84.6°

average daily high. The coldest month is January, averaging a low of 12.5°F.

Marion County gets 37.45" of precipitation a year, and 40% of it falls in May, Jun, Jul.

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	29.9°	12.5°	1.15"
February	35.1°	17.0°	1.67"
March	47.6°	27.6°	1.87"
April	60.6°	39.2°	3.85"
May	70.9°	51.2°	4.98"
June	80.6°	61.3°	5.61"
July	84.6°	65.6°	4.34"
August	82.7°	63.1°	3.89"
September	76.2°	54.3°	3.66"
October	63.0°	42.2°	3.06"
November	48.1°	29.9°	1.80"
December	35.5°	18.9°	1.57"

Rainfall by month

Precipitation is spread fairly evenly through the year here, with 40% falling in the wettest three months (May, Jun, Jul).

January 1.15"

February 1.67"

March 1.87"

April 3.85"

May 4.98"

June 5.61"

July 4.34"

August 3.89"

September 3.66"

October 3.06"

November 1.80"

December 1.57"

Annual total 37.45"

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 950

Heating degree days How much heating the climate demands 6,416

Approximate annual cooling cost At 14.14¢/kWh, Iowa average $134

Approximate annual electric heating cost Lower where heating is gas rather than electric $318

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 Marion County, where electricity is one line of eight.

Common questions

What is the weather like in Marion County?

Marion County averages a high of 84.6°F in July and a low of 12.5°F in January. Annual precipitation is 37.45 inches, with essentially no snow.

When is the rainy season in Marion County?

The wettest stretch is May, Jun, Jul, which accounts for 40% of the year's precipitation. Precipitation is relatively evenly distributed across the year.

How hot does it get in Marion County?

The average daily high in July, the hottest month, is 84.6°F. That drives 950 cooling degree days a year, which is what your air conditioning has to work against.

Does it snow in Marion County?

Effectively no. Measurable snowfall is rare in Marion County.

Sources

Temperature, precipitation and snowfall normals — NOAA National Centers for Environmental Information, 1991–2020 Monthly Climate Normals, station KNOXVILLE, IA US (USC00134502), 0.6 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, Iowa residential average.
Wet-season share is the wettest three consecutive months as a percentage of annual precipitation, calculated from the monthly normals.