Green River climate

Green River Frost Dates and Growing Season

NOAA 1991-2020 normals for Moab Canyonland AP, 44.3 km from Green River, elevation 4561 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Moab Canyonland AP. 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 April 22 and the first fall freeze around October 20, a growing season of about 179 days.

Median at 36°F
last May 3, first October 10
Median at 32°F
last April 22, first October 20
Median at 28°F
last April 8, first October 30

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 20May 13May 9May 5May 3Apr 30Apr 28Apr 25Apr 20
32°FMay 8May 3Apr 29Apr 26Apr 22Apr 20Apr 16Apr 12Apr 7
28°FApr 27Apr 21Apr 16Apr 11Apr 8Apr 5Apr 2Mar 29Mar 21
24°FApr 11Apr 5Apr 1Mar 28Mar 23Mar 19Mar 13Mar 9Mar 2
20°FMar 25Mar 15Mar 9Mar 5Mar 2Feb 28Feb 24Feb 18Feb 12
16°FMar 6Mar 1Feb 25Feb 19Feb 16Feb 12Feb 7Feb 2Jan 26

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 28Oct 2Oct 5Oct 7Oct 10Oct 13Oct 15Oct 18Oct 22
32°FOct 6Oct 10Oct 14Oct 17Oct 20Oct 22Oct 25Oct 28Nov 1
28°FOct 15Oct 20Oct 24Oct 27Oct 30Nov 1Nov 4Nov 6Nov 9
24°FOct 25Oct 30Nov 3Nov 5Nov 7Nov 9Nov 11Nov 14Nov 18
20°FNov 3Nov 7Nov 10Nov 13Nov 15Nov 18Nov 19Nov 22Nov 27
16°FNov 9Nov 14Nov 18Nov 21Nov 24Nov 26Nov 30Dec 4Dec 10

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°F175170166162158155151146138
32°F199193188184179176171167159
28°F224217211206202197193187179
24°F250242236231226222217211204
20°F278270263259255250244238230
16°F306296290284279273268263256

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
5,376
Cooling degree days, base 65°F
1,415
Growing degree days, base 40°F
6,227
Growing degree days, base 45°F
4,981
Growing degree days, base 50°F
3,883
Growing degree days, base 55°F
2,931
Growing degree days, base 60°F
2,112

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,14500
February81602
March592039
April3603143
May13570406
June15287722
July0500965
August1402866
September45145551
October3447178
November765011
December1,15700

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 44.3 km from Green River. 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 USW00093075 (Moab Canyonland AP). Public domain.