Grantsville climate

Grantsville Frost Dates and Growing Season

NOAA 1991-2020 normals for Grantsville 2W, 3.7 km from Grantsville, elevation 4550 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Grantsville 2W. 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 2 and the first fall freeze around October 14, a growing season of about 164 days.

Median at 36°F
last May 16, first October 4
Median at 32°F
last May 2, first October 14
Median at 28°F
last April 17, first October 25

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

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 21Sep 26Sep 29Oct 1Oct 4Oct 6Oct 8Oct 12Oct 17
32°FSep 30Oct 4Oct 8Oct 11Oct 14Oct 17Oct 20Oct 23Oct 27
28°FOct 8Oct 14Oct 18Oct 22Oct 25Oct 28Oct 31Nov 2Nov 8
24°FOct 19Oct 26Oct 30Nov 1Nov 5Nov 8Nov 12Nov 15Nov 20
20°FOct 31Nov 4Nov 9Nov 13Nov 16Nov 19Nov 22Nov 25Nov 29
16°FNov 8Nov 14Nov 18Nov 22Nov 24Nov 27Nov 30Dec 5Dec 11

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°F160153148144140136130124116
32°F183176172168164160155150141
28°F213205198193189184178173164
24°F243235229223217212206199190
20°F272264259253248242237230219
16°F294286280276270266261254246

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
6,044
Cooling degree days, base 65°F
1,033
Growing degree days, base 40°F
5,290
Growing degree days, base 45°F
4,130
Growing degree days, base 50°F
3,142
Growing degree days, base 55°F
2,313
Growing degree days, base 60°F
1,616

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,14200
February89501
March721017
April510166
May25733266
June60158550
July2403866
August4345806
September10989438
October4364121
November797012
December1,11301

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 3.7 km from Grantsville. 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 USC00423348 (Grantsville 2W). Public domain.