De Smet climate

De Smet Frost Dates and Growing Season

NOAA 1991-2020 normals for De Smet, 0.6 km from De Smet, elevation 1705 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for De Smet. 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 4, a growing season of about 151 days.

Median at 36°F
last May 16, first September 26
Median at 32°F
last May 5, first October 4
Median at 28°F
last April 28, first October 14

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 30May 26May 22May 19May 16May 13May 10May 7May 3
32°FMay 20May 14May 11May 8May 5May 3Apr 30Apr 27Apr 22
28°FMay 10May 5May 2Apr 30Apr 28Apr 24Apr 21Apr 16Apr 11
24°FMay 2Apr 28Apr 23Apr 19Apr 15Apr 12Apr 8Apr 5Apr 2
20°FApr 22Apr 18Apr 13Apr 9Apr 7Apr 4Apr 1Mar 28Mar 20
16°FApr 15Apr 8Apr 4Apr 2Mar 31Mar 27Mar 22Mar 17Mar 12

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 19Sep 22Sep 24Sep 26Sep 29Oct 1Oct 5Oct 8
32°FSep 23Sep 27Sep 30Oct 2Oct 4Oct 7Oct 10Oct 14Oct 17
28°FSep 30Oct 4Oct 8Oct 11Oct 14Oct 17Oct 20Oct 23Oct 27
24°FOct 8Oct 13Oct 17Oct 20Oct 23Oct 25Oct 28Nov 1Nov 5
20°FOct 18Oct 23Oct 27Oct 30Nov 1Nov 3Nov 6Nov 9Nov 14
16°FOct 27Oct 31Nov 3Nov 6Nov 8Nov 11Nov 14Nov 17Nov 22

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°F150144139136133129125121114
32°F170164159155151147143138131
28°F189182177173169164161156149
24°F208201196192188184180175167
20°F227220215211206202198192186
16°F244238232227224220215209202

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
8,152
Cooling degree days, base 65°F
547
Growing degree days, base 40°F
4,338
Growing degree days, base 45°F
3,344
Growing degree days, base 50°F
2,461
Growing degree days, base 55°F
1,695
Growing degree days, base 60°F
1,051

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,57900
February1,29200
March1,06207
April628154
May29423237
June62107496
July15209659
August28152589
September17652339
October580376
November1,01005
December1,42600

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 0.6 km from De Smet. 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 USC00392302 (De Smet). Public domain.