Duchesne County climate

Duchesne County Frost Dates and Growing Season

NOAA 1991-2020 normals for Altamont, 13.2 km from Duchesne County, elevation 6456 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Altamont. 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 31 and the first fall freeze around September 23, a growing season of about 112 days.

Median at 36°F
last June 13, first September 15
Median at 32°F
last May 31, first September 23
Median at 28°F
last May 17, first October 1

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 29Jun 23Jun 19Jun 16Jun 13Jun 9Jun 7Jun 3May 30
32°FJun 16Jun 10Jun 5Jun 2May 31May 28May 24May 20May 16
28°FJun 4May 30May 25May 20May 17May 14May 9May 6May 1
24°FMay 19May 13May 9May 5May 2Apr 30Apr 26Apr 23Apr 19
20°FMay 6May 1Apr 27Apr 24Apr 21Apr 18Apr 14Apr 10Apr 4
16°FApr 23Apr 17Apr 13Apr 9Apr 5Apr 1Mar 28Mar 22Mar 14

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 9Sep 12Sep 15Sep 17Sep 20Sep 23Sep 26
32°FSep 6Sep 13Sep 16Sep 20Sep 23Sep 25Sep 28Oct 1Oct 5
28°FSep 17Sep 23Sep 27Sep 30Oct 1Oct 4Oct 7Oct 11Oct 16
24°FSep 29Oct 2Oct 6Oct 9Oct 13Oct 16Oct 18Oct 23Oct 28
20°FOct 10Oct 15Oct 19Oct 22Oct 25Oct 27Oct 30Nov 3Nov 8
16°FOct 18Oct 24Oct 27Oct 31Nov 3Nov 6Nov 9Nov 14Nov 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°F11110499969187827670
32°F1331261221161121081039990
28°F158151146141136132127120113
24°F182176172167162158154149140
20°F208201195190186181177173165
16°F237227221215210205200195188

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
8,450
Cooling degree days, base 65°F
182
Growing degree days, base 40°F
3,336
Growing degree days, base 45°F
2,415
Growing degree days, base 50°F
1,641
Growing degree days, base 55°F
1,004
Growing degree days, base 60°F
512

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,46300
February1,17200
March96301
April715013
May4601101
June18723299
July3898526
August5555465
September2714210
October662026
November1,03500
December1,42900

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 13.2 km from Duchesne County. 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 USC00420074 (Altamont). Public domain.