30-year climate normals

Jefferson County Climate and Weather Averages

Hottest month — July

86.6°

average daily high. The coldest month is January, averaging a low of 12.1°F.

Jefferson County gets 10.07" of precipitation a year, and 37% 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	28.7°	12.1°	0.67"
February	34.2°	15.7°	0.56"
March	47.2°	25.3°	0.81"
April	57.5°	31.4°	1.03"
May	67.2°	38.4°	1.57"
June	76.2°	44.6°	1.09"
July	86.6°	49.3°	0.46"
August	85.6°	47.5°	0.59"
September	74.8°	40.6°	0.97"
October	59.1°	30.8°	0.88"
November	43.0°	21.9°	0.66"
December	30.3°	13.4°	0.78"

Rainfall by month

Precipitation is spread fairly evenly through the year here, with 37% falling in the wettest three months (Apr, May, Jun).

January 0.67"

February 0.56"

March 0.81"

April 1.03"

May 1.57"

June 1.09"

July 0.46"

August 0.59"

September 0.97"

October 0.88"

November 0.66"

December 0.78"

Annual total 10.07"

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 249

Heating degree days How much heating the climate demands 7,792

Approximate annual cooling cost At 12.35¢/kWh, Idaho average $31

Approximate annual electric heating cost Lower where heating is gas rather than electric $337

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 Jefferson County, where electricity is one line of eight.

Common questions

What is the weather like in Jefferson County?

Jefferson County averages a high of 86.6°F in July and a low of 12.1°F in January. Annual precipitation is 10.07 inches, with essentially no snow.

When is the rainy season in Jefferson County?

The wettest stretch is Apr, May, Jun, which accounts for 37% of the year's precipitation. Precipitation is relatively evenly distributed across the year.

How hot does it get in Jefferson County?

The average daily high in July, the hottest month, is 86.6°F. That drives 249 cooling degree days a year, which is what your air conditioning has to work against.

Does it snow in Jefferson County?

Effectively no. Measurable snowfall is rare in Jefferson County.

Sources

Temperature, precipitation and snowfall normals — NOAA National Centers for Environmental Information, 1991–2020 Monthly Climate Normals, station IDAHO FALLS FANNING FLD, ID US (USW00024145), 23.1 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, Idaho residential average.
Wet-season share is the wettest three consecutive months as a percentage of annual precipitation, calculated from the monthly normals.