Moorcroft climate

Moorcroft Frost Dates and Growing Season

NOAA 1991-2020 normals for Moorcroft 3S, 5.4 km from Moorcroft, elevation 4325 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Moorcroft 3S. 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 22 and the first fall freeze around September 28, a growing season of about 127 days.

Median at 36°F
last June 1, first September 16
Median at 32°F
last May 22, first September 28
Median at 28°F
last May 10, first October 5

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 28Jun 16Jun 8Jun 4Jun 1May 30May 27May 23May 18
32°FJun 9Jun 2May 29May 25May 22May 19May 16May 12May 8
28°FMay 27May 21May 17May 13May 10May 7May 4May 1Apr 27
24°FMay 14May 8May 4May 1Apr 29Apr 25Apr 22Apr 17Apr 12
20°FMay 4Apr 30Apr 25Apr 20Apr 16Apr 12Apr 9Apr 4Mar 30
16°FApr 25Apr 17Apr 14Apr 10Apr 6Apr 1Mar 29Mar 22Mar 13

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

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°F127119114109105100958877
32°F148142136132127123118112102
28°F167162157153149144139133125
24°F190182177172168164159154146
20°F214205200195189185179173165
16°F237228221214209203199194185

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
7,906
Cooling degree days, base 65°F
490
Growing degree days, base 40°F
3,959
Growing degree days, base 45°F
2,986
Growing degree days, base 50°F
2,156
Growing degree days, base 55°F
1,465
Growing degree days, base 60°F
906

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,33300
February1,16200
March95706
April713025
May4393129
June14658370
July21219663
August41173597
September22035290
October607167
November96709
December1,30000

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 5.4 km from Moorcroft. 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 USW00024088 (Moorcroft 3S). Public domain.