Chadron climate

Chadron Frost Dates and Growing Season

NOAA 1991-2020 normals for Chadron 3SW, 4.9 km from Chadron, elevation 3383 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Chadron 3SW. 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 15 and the first fall freeze around September 28, a growing season of about 133 days.

Median at 36°F
last May 26, first September 18
Median at 32°F
last May 15, first September 28
Median at 28°F
last May 5, first October 7

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

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°F1321261211171121081039991
32°F151145141136133129125120113
28°F173167161158154150146141134
24°F195187181177174169164159151
20°F217209203198193189184180172
16°F238230224218213208204198191

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
6,905
Cooling degree days, base 65°F
746
Growing degree days, base 40°F
4,769
Growing degree days, base 45°F
3,682
Growing degree days, base 50°F
2,744
Growing degree days, base 55°F
1,948
Growing degree days, base 60°F
1,282

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,22900
February1,04402
March860021
April596160
May31520225
June73115494
July8285742
August22246690
September15474386
October5255108
November876016
December1,20301

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 4.9 km from Chadron. 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 USC00251575 (Chadron 3SW). Public domain.