Belle Fourche climate

Belle Fourche Frost Dates and Growing Season

NOAA 1991-2020 normals for Belle Fourche, 0.1 km from Belle Fourche, elevation 3020 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Belle Fourche. 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 10 and the first fall freeze around September 30, a growing season of about 143 days.

Median at 36°F
last May 21, first September 21
Median at 32°F
last May 10, first September 30
Median at 28°F
last April 30, first October 10

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 27May 24May 21May 19May 16May 13May 8
32°FMay 25May 20May 16May 13May 10May 7May 4May 1Apr 27
28°FMay 15May 9May 5May 2Apr 30Apr 26Apr 23Apr 20Apr 14
24°FMay 6Apr 29Apr 25Apr 21Apr 17Apr 14Apr 10Apr 7Apr 2
20°FApr 27Apr 20Apr 15Apr 11Apr 8Apr 5Apr 2Mar 30Mar 21
16°FApr 16Apr 10Apr 6Apr 3Apr 1Mar 29Mar 23Mar 17Mar 10

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 8Sep 13Sep 17Sep 19Sep 21Sep 23Sep 26Sep 30Oct 4
32°FSep 16Sep 21Sep 24Sep 27Sep 30Oct 3Oct 5Oct 9Oct 13
28°FSep 23Sep 29Oct 2Oct 6Oct 10Oct 13Oct 16Oct 20Oct 24
24°FOct 1Oct 8Oct 14Oct 17Oct 20Oct 23Oct 26Oct 29Nov 3
20°FOct 13Oct 20Oct 23Oct 26Oct 29Nov 1Nov 4Nov 7Nov 13
16°FOct 22Oct 27Oct 31Nov 3Nov 6Nov 9Nov 13Nov 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°F143135130126122118113109101
32°F161155151147143139135129120
28°F184176171166163158154149141
24°F205199194189184179175168161
20°F225217211206202198192186178
16°F246238231225219215209204195

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
6,902
Cooling degree days, base 65°F
695
Growing degree days, base 40°F
4,745
Growing degree days, base 45°F
3,638
Growing degree days, base 50°F
2,693
Growing degree days, base 55°F
1,890
Growing degree days, base 60°F
1,223

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,24901
February1,06102
March874018
April574161
May29920229
June63108496
July10273728
August19227673
September14762375
October512499
November88409
December1,20901

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 0.1 km from Belle Fourche. 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 USC00390559 (Belle Fourche). Public domain.