Otter Tail County climate

Otter Tail County Frost Dates and Growing Season

NOAA 1991-2020 normals for Ottertail, 12.4 km from Otter Tail County, elevation 1349 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ottertail. 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 5 and the first fall freeze around October 5, a growing season of about 153 days.

Median at 36°F
last May 14, first September 27
Median at 32°F
last May 5, first October 5
Median at 28°F
last April 28, 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°FMay 27May 24May 20May 17May 14May 11May 9May 6May 2
32°FMay 18May 14May 10May 8May 5May 3May 1Apr 29Apr 24
28°FMay 10May 5May 2Apr 30Apr 28Apr 25Apr 21Apr 18Apr 13
24°FMay 2Apr 28Apr 24Apr 20Apr 17Apr 15Apr 12Apr 9Apr 5
20°FApr 24Apr 19Apr 15Apr 12Apr 10Apr 7Apr 5Apr 2Mar 31
16°FApr 17Apr 11Apr 8Apr 5Apr 3Apr 1Mar 31Mar 26Mar 21

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 15Sep 20Sep 22Sep 24Sep 27Sep 29Oct 1Oct 4Oct 8
32°FSep 23Sep 27Sep 30Oct 2Oct 5Oct 7Oct 10Oct 13Oct 19
28°FOct 1Oct 5Oct 8Oct 12Oct 15Oct 19Oct 22Oct 24Oct 29
24°FOct 9Oct 16Oct 21Oct 24Oct 26Oct 30Nov 1Nov 5Nov 9
20°FOct 22Oct 26Oct 30Nov 1Nov 4Nov 7Nov 10Nov 13Nov 18
16°FOct 29Nov 2Nov 5Nov 8Nov 11Nov 14Nov 16Nov 20Nov 25

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°F152146141137135131127123117
32°F169164160156153149145141136
28°F189182178174171166162158152
24°F208202198194190186182177170
20°F225218214209206202199194187
16°F240232227223219215212208201

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
9,147
Cooling degree days, base 65°F
416
Growing degree days, base 40°F
3,944
Growing degree days, base 45°F
3,012
Growing degree days, base 50°F
2,187
Growing degree days, base 55°F
1,472
Growing degree days, base 60°F
878

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,77600
February1,47000
March1,22502
April731127
May34318199
June7983456
July19156601
August31124558
September21534287
October634156
November1,08203
December1,54200

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 12.4 km from Otter Tail 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 USC00216276 (Ottertail). Public domain.