Laramie climate

Laramie Frost Dates and Growing Season

NOAA 1991-2020 normals for Laramie 4SE, 5.7 km from Laramie, elevation 7390 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Laramie 4SE. 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 126 days.

Median at 36°F
last June 3, first September 19
Median at 32°F
last May 22, first September 28
Median at 28°F
last May 12, 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 17Jun 13Jun 9Jun 5Jun 3May 31May 29May 25May 22
32°FJun 4Jun 1May 29May 25May 22May 20May 17May 14May 10
28°FMay 25May 20May 16May 14May 12May 9May 6May 3Apr 30
24°FMay 14May 11May 8May 5May 2Apr 30Apr 27Apr 23Apr 18
20°FMay 8May 2Apr 29Apr 25Apr 22Apr 18Apr 14Apr 9Apr 3
16°FApr 30Apr 22Apr 17Apr 11Apr 7Apr 4Mar 31Mar 26Mar 20

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 5Sep 11Sep 14Sep 17Sep 19Sep 21Sep 24Sep 26Sep 30
32°FSep 16Sep 20Sep 23Sep 25Sep 28Sep 30Oct 2Oct 5Oct 9
28°FSep 22Sep 27Sep 30Oct 3Oct 5Oct 8Oct 11Oct 14Oct 18
24°FOct 1Oct 5Oct 8Oct 11Oct 14Oct 17Oct 19Oct 23Oct 27
20°FOct 8Oct 13Oct 17Oct 20Oct 23Oct 26Oct 29Nov 2Nov 7
16°FOct 17Oct 21Oct 26Oct 30Nov 2Nov 5Nov 9Nov 13Nov 17

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°F122117113109106102999487
32°F143138134130126123119114108
28°F163157153149146142138132126
24°F182176171167163159156151145
20°F207199193189183178174168161
16°F231223217211207201195189179

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
8,150
Cooling degree days, base 65°F
155
Growing degree days, base 40°F
3,356
Growing degree days, base 45°F
2,426
Growing degree days, base 50°F
1,641
Growing degree days, base 55°F
989
Growing degree days, base 60°F
487

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,31100
February1,11800
March1,00602
April778013
May522183
June18820291
July3178512
August6846443
September2349247
October662047
November95703
December1,27400

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 5.7 km from Laramie. 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 USC00485417 (Laramie 4SE). Public domain.