Eagle Butte climate

Eagle Butte Frost Dates and Growing Season

NOAA 1991-2020 normals for Dupree 15 Sse, 23.9 km from Eagle Butte, elevation 2100 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Dupree 15 Sse. 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 6 and the first fall freeze around October 2, a growing season of about 148 days.

Median at 36°F
last May 17, first September 25
Median at 32°F
last May 6, first October 2
Median at 28°F
last April 27, first October 11

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 25May 22May 19May 17May 14May 11May 8May 5
32°FMay 20May 16May 12May 9May 6May 4May 2Apr 28Apr 24
28°FMay 10May 5May 2Apr 30Apr 27Apr 24Apr 21Apr 18Apr 14
24°FApr 30Apr 26Apr 22Apr 19Apr 16Apr 13Apr 10Apr 7Apr 4
20°FApr 22Apr 17Apr 13Apr 10Apr 8Apr 6Apr 3Mar 31Mar 23
16°FApr 15Apr 10Apr 6Apr 4Apr 1Mar 29Mar 24Mar 20Mar 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 11Sep 17Sep 20Sep 22Sep 25Sep 27Sep 29Oct 2Oct 7
32°FSep 20Sep 24Sep 28Sep 30Oct 2Oct 5Oct 7Oct 11Oct 16
28°FSep 28Oct 2Oct 5Oct 8Oct 11Oct 15Oct 18Oct 21Oct 25
24°FOct 5Oct 10Oct 14Oct 18Oct 20Oct 23Oct 26Oct 29Nov 2
20°FOct 14Oct 19Oct 23Oct 26Oct 29Nov 1Nov 4Nov 8Nov 13
16°FOct 22Oct 28Oct 31Nov 3Nov 6Nov 9Nov 13Nov 18Nov 23

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°F147142137134131126123117111
32°F166160156152148144140135130
28°F184178174169166162158153146
24°F204197192187183180176171165
20°F224216211206201197192188181
16°F244236229223218214209204196

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
7,680
Cooling degree days, base 65°F
741
Growing degree days, base 40°F
4,640
Growing degree days, base 45°F
3,612
Growing degree days, base 50°F
2,706
Growing degree days, base 55°F
1,926
Growing degree days, base 60°F
1,267

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,44100
February1,20801
March1,003012
April621160
May30722229
June71107487
July11275728
August21249693
September16181386
October557699
November954010
December1,32500

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 23.9 km from Eagle Butte. 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 USC00392446 (Dupree 15 Sse). Public domain.