Star Valley climate

Star Valley Frost Dates and Growing Season

NOAA 1991-2020 normals for Payson, 8.4 km from Star Valley, elevation 4850 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Payson. 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 29 and the first fall freeze around October 24, a growing season of about 176 days.

Median at 36°F
last May 15, first October 14
Median at 32°F
last April 29, first October 24
Median at 28°F
last April 10, first November 6

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 4May 31May 24May 19May 15May 11May 7May 3Apr 29
32°FMay 20May 12May 7May 2Apr 29Apr 26Apr 22Apr 18Apr 13
28°FMay 1Apr 24Apr 18Apr 13Apr 10Apr 6Apr 3Mar 30Mar 20
24°FApr 12Apr 5Mar 29Mar 23Mar 16Mar 11Mar 7Mar 2Feb 23
20°FMar 19Mar 10Mar 5Mar 1Feb 24Feb 19Feb 13Feb 6Jan 26
16°FFeb 28Feb 20Feb 12Feb 4Jan 29Jan 20Jan 13Jan 4Dec 24

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°FOct 1Oct 5Oct 8Oct 11Oct 14Oct 16Oct 18Oct 22Oct 27
32°FOct 11Oct 15Oct 19Oct 22Oct 24Oct 28Nov 1Nov 4Nov 8
28°FOct 21Oct 26Oct 31Nov 3Nov 6Nov 10Nov 13Nov 16Nov 21
24°FNov 1Nov 6Nov 11Nov 15Nov 18Nov 21Nov 24Nov 28Dec 2
20°FNov 13Nov 19Nov 23Nov 27Dec 1Dec 4Dec 9Dec 13Dec 21
16°FNov 24Dec 1Dec 6Dec 11Dec 15Dec 22Dec 27Jan 2Jan 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°F172164160155150145140135127
32°F198191186181176172167161153
28°F233224219213208203197190180
24°F274263255248243237230223213
20°F313302296288281274268259246
16°F360349339332326317309299288

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
93% 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
3,892
Cooling degree days, base 65°F
1,004
Growing degree days, base 40°F
6,410
Growing degree days, base 45°F
4,897
Growing degree days, base 50°F
3,626
Growing degree days, base 55°F
2,572
Growing degree days, base 60°F
1,702

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January74301
February61306
March516047
April3360142
May14331357
June15180615
July0341806
August0306770
September20137567
October2189267
November521049
December76701

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 8.4 km from Star Valley. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USW00093139 (Payson). Public domain.