30-year climate normals

Union County Climate and Weather Averages

Hottest month — July

85.5°

average daily high. The coldest month is January, averaging a low of 10.2°F.

Union County gets 28" of precipitation a year, and 42% 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	30.5°	10.2°	0.53"
February	36.1°	14.0°	0.70"
March	48.4°	25.2°	1.42"
April	61.9°	36.0°	3.09"
May	72.7°	48.1°	3.96"
June	82.2°	59.1°	4.30"
July	85.5°	63.2°	3.61"
August	83.3°	60.7°	2.88"
September	78.1°	51.8°	3.07"
October	64.6°	38.5°	2.35"
November	48.2°	25.2°	1.30"
December	34.0°	14.6°	0.79"

Rainfall by month

Precipitation is spread fairly evenly through the year here, with 42% falling in the wettest three months (May, Jun, Jul).

January 0.53"

February 0.70"

March 1.42"

April 3.09"

May 3.96"

June 4.30"

July 3.61"

August 2.88"

September 3.07"

October 2.35"

November 1.30"

December 0.79"

Annual total 28"

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 904

Heating degree days How much heating the climate demands 6,758

Approximate annual cooling cost At 15.73¢/kWh, South Dakota average $142

Approximate annual electric heating cost Lower where heating is gas rather than electric $372

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 Union County, where electricity is one line of eight.

Common questions

What is the weather like in Union County?

Union County averages a high of 85.5°F in July and a low of 10.2°F in January. Annual precipitation is 28 inches, with essentially no snow.

When is the rainy season in Union County?

The wettest stretch is May, Jun, Jul, which accounts for 42% of the year's precipitation. Precipitation is relatively evenly distributed across the year.

How hot does it get in Union County?

The average daily high in July, the hottest month, is 85.5°F. That drives 904 cooling degree days a year, which is what your air conditioning has to work against.

Does it snow in Union County?

Effectively no. Measurable snowfall is rare in Union County.

Sources

Temperature, precipitation and snowfall normals — NOAA National Centers for Environmental Information, 1991–2020 Monthly Climate Normals, station VERMILLION 2 SE, SD US (USC00398622), 14.4 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, South Dakota residential average.
Wet-season share is the wettest three consecutive months as a percentage of annual precipitation, calculated from the monthly normals.