Mandan climate

Mandan Frost Dates and Growing Season

NOAA 1991-2020 normals for Mandan Exp Stn, 2.2 km from Mandan, elevation 1750 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mandan Exp Stn. 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 13 and the first fall freeze around September 27, a growing season of about 136 days.

Median at 36°F
last May 23, first September 19
Median at 32°F
last May 13, first September 27
Median at 28°F
last May 3, first October 4

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 4May 31May 28May 25May 23May 20May 17May 14May 10
32°FMay 26May 21May 18May 15May 13May 10May 7May 4May 1
28°FMay 17May 13May 9May 6May 3Apr 30Apr 28Apr 24Apr 19
24°FMay 7May 2Apr 29Apr 26Apr 23Apr 20Apr 17Apr 13Apr 9
20°FApr 28Apr 23Apr 19Apr 17Apr 14Apr 11Apr 8Apr 6Apr 2
16°FApr 20Apr 15Apr 11Apr 8Apr 6Apr 3Apr 1Mar 28Mar 20

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 6Sep 10Sep 14Sep 16Sep 19Sep 21Sep 24Sep 26Oct 1
32°FSep 15Sep 20Sep 23Sep 25Sep 27Sep 30Oct 2Oct 5Oct 10
28°FSep 23Sep 27Sep 30Oct 2Oct 4Oct 7Oct 10Oct 14Oct 19
24°FSep 30Oct 4Oct 7Oct 11Oct 14Oct 17Oct 20Oct 23Oct 27
20°FOct 7Oct 13Oct 18Oct 21Oct 24Oct 27Oct 30Nov 1Nov 7
16°FOct 19Oct 24Oct 28Oct 31Nov 2Nov 5Nov 8Nov 11Nov 16

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°F136130126122119115111106101
32°F154148144140136133129124118
28°F173166162158154150146141135
24°F192186181177173168164159151
20°F211204199196192188184179172
16°F230224218214209205200196189

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
8,674
Cooling degree days, base 65°F
482
Growing degree days, base 40°F
4,032
Growing degree days, base 45°F
3,079
Growing degree days, base 50°F
2,242
Growing degree days, base 55°F
1,525
Growing degree days, base 60°F
933

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,62400
February1,35100
March1,11805
April683139
May34016201
June9378437
July24188629
August44157579
September22342293
October649157
November1,06503
December1,46000

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 2.2 km from Mandan. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00325479 (Mandan Exp Stn). Public domain.