Benson County climate

Benson County Frost Dates and Growing Season

NOAA 1991-2020 normals for Minnewaukan, 7.5 km from Benson County, elevation 1470 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Minnewaukan. 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 12 and the first fall freeze around September 29, a growing season of about 138 days.

Median at 36°F
last May 20, first September 21
Median at 32°F
last May 12, first September 29
Median at 28°F
last May 4, first October 8

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°FMay 31May 28May 25May 23May 20May 18May 15May 12May 9
32°FMay 25May 20May 17May 14May 12May 9May 7May 4May 1
28°FMay 16May 12May 8May 6May 4May 1Apr 29Apr 24Apr 19
24°FMay 8May 4May 1Apr 29Apr 26Apr 22Apr 19Apr 15Apr 9
20°FMay 1Apr 27Apr 22Apr 19Apr 16Apr 12Apr 9Apr 5Apr 2
16°FApr 23Apr 17Apr 13Apr 10Apr 7Apr 4Apr 2Mar 31Mar 24

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 16Sep 18Sep 21Sep 23Sep 26Sep 29Oct 2
32°FSep 17Sep 21Sep 24Sep 27Sep 29Oct 1Oct 4Oct 7Oct 12
28°FSep 25Sep 30Oct 3Oct 5Oct 8Oct 11Oct 14Oct 18Oct 21
24°FOct 3Oct 9Oct 13Oct 16Oct 18Oct 21Oct 23Oct 26Oct 31
20°FOct 14Oct 18Oct 22Oct 25Oct 27Oct 30Nov 1Nov 4Nov 9
16°FOct 22Oct 26Oct 29Nov 1Nov 3Nov 5Nov 9Nov 12Nov 17

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°F137132128126122119116111105
32°F155150146142138135132128122
28°F175169164160156152149144139
24°F193187182178174170167162155
20°F213207201197192188184180172
16°F229221216212209204200194189

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
9,598
Cooling degree days, base 65°F
348
Growing degree days, base 40°F
3,682
Growing degree days, base 45°F
2,783
Growing degree days, base 50°F
1,992
Growing degree days, base 55°F
1,312
Growing degree days, base 60°F
754

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,78900
February1,50400
March1,29101
April774020
May3778166
June10263413
July31139573
August51110524
September25126252
October689142
November1,14501
December1,59500

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 7.5 km from Benson 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 USC00325848 (Minnewaukan). Public domain.