Twin Falls County climate

Twin Falls County Frost Dates and Growing Season

NOAA 1991-2020 normals for Twin Falls Sun Vly Rgnl AP, 20.4 km from Twin Falls County, elevation 4151 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Twin Falls Sun Vly Rgnl AP. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around May 9 and the first fall freeze around October 4, a growing season of about 147 days.

Median at 36°F
last May 28, first September 23
Median at 32°F
last May 9, first October 4
Median at 28°F
last April 25, first October 15

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°FJun 16Jun 11Jun 5Jun 1May 28May 24May 19May 15May 10
32°FMay 28May 21May 15May 12May 9May 5May 2Apr 29Apr 25
28°FMay 11May 5May 1Apr 27Apr 25Apr 21Apr 18Apr 14Apr 8
24°FApr 25Apr 17Apr 12Apr 8Apr 5Apr 1Mar 28Mar 21Mar 12
20°FApr 7Mar 31Mar 24Mar 17Mar 12Mar 7Mar 3Feb 26Feb 18
16°FMar 12Mar 6Mar 2Feb 28Feb 23Feb 19Feb 14Feb 10Feb 4

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°FSep 9Sep 13Sep 17Sep 20Sep 23Sep 26Sep 28Oct 1Oct 5
32°FSep 20Sep 25Sep 28Oct 1Oct 4Oct 7Oct 11Oct 15Oct 20
28°FSep 29Oct 3Oct 7Oct 11Oct 15Oct 18Oct 21Oct 25Oct 30
24°FOct 8Oct 15Oct 19Oct 22Oct 26Oct 29Nov 1Nov 5Nov 12
20°FOct 19Oct 24Oct 29Nov 1Nov 5Nov 9Nov 12Nov 17Nov 23
16°FOct 30Nov 4Nov 9Nov 12Nov 16Nov 20Nov 24Nov 28Dec 4

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F13913012512011511010610093
32°F170163156151147142137132122
28°F198190184178174169164157148
24°F233221214208204198193186178
20°F264256250244238232226217206
16°F291284277271266260255249239

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
100% of years
16°F or colder
100% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
6,387
Cooling degree days, base 65°F
617
Growing degree days, base 40°F
4,570
Growing degree days, base 45°F
3,456
Growing degree days, base 50°F
2,521
Growing degree days, base 55°F
1,747
Growing degree days, base 60°F
1,116

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,11400
February90200
March746010
April555046
May31115205
June11074418
July10259714
August17212660
September15153364
October488396
November85207
December1,13100

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 20.4 km from Twin Falls County. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USW00094178 (Twin Falls Sun Vly Rgnl AP). Public domain.