Mitchell climate

Mitchell Frost Dates and Growing Season

NOAA 1991-2020 normals for Mitchell, 7 km from Mitchell, elevation 1287 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mitchell. 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 April 27 and the first fall freeze around October 11, a growing season of about 167 days.

Median at 36°F
last May 5, first October 2
Median at 32°F
last April 27, first October 11
Median at 28°F
last April 17, first October 21

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 19May 15May 11May 8May 5May 3Apr 30Apr 27Apr 22
32°FMay 10May 5May 2Apr 30Apr 27Apr 24Apr 21Apr 17Apr 12
28°FMay 1Apr 27Apr 23Apr 20Apr 17Apr 14Apr 10Apr 7Apr 3
24°FApr 22Apr 17Apr 14Apr 10Apr 8Apr 5Apr 2Mar 29Mar 22
20°FApr 15Apr 9Apr 4Apr 2Mar 31Mar 27Mar 22Mar 17Mar 13
16°FApr 6Mar 31Mar 27Mar 23Mar 20Mar 16Mar 13Mar 10Mar 5

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 21Sep 25Sep 28Sep 30Oct 2Oct 4Oct 7Oct 11Oct 15
32°FSep 30Oct 2Oct 5Oct 8Oct 11Oct 14Oct 17Oct 20Oct 23
28°FOct 5Oct 12Oct 16Oct 18Oct 21Oct 24Oct 26Oct 30Nov 4
24°FOct 16Oct 21Oct 25Oct 28Oct 31Nov 2Nov 5Nov 9Nov 13
20°FOct 25Oct 30Nov 1Nov 4Nov 7Nov 10Nov 14Nov 17Nov 22
16°FNov 1Nov 5Nov 9Nov 12Nov 15Nov 18Nov 22Nov 25Nov 29

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°F167161156152148145141137131
32°F185180175171167164159155149
28°F205198193189186182178171165
24°F226218213209204200196192185
20°F244237231226222217212207200
16°F260253247243238233228222214

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
7,122
Cooling degree days, base 65°F
940
Growing degree days, base 40°F
5,172
Growing degree days, base 45°F
4,098
Growing degree days, base 50°F
3,132
Growing degree days, base 55°F
2,278
Growing degree days, base 60°F
1,548

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,44800
February1,17901
March926119
April527387
May21645316
June28184606
July2348810
August8258715
September10895441
October4727127
November89609
December1,31300

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 km from Mitchell. 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 USC00395669 (Mitchell). Public domain.