Midvale climate

Midvale Frost Dates and Growing Season

NOAA 1991-2020 normals for Cottonwood Weir, 9.9 km from Midvale, elevation 4986 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cottonwood Weir. 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 22, a growing season of about 174 days.

Median at 36°F
last May 13, first October 11
Median at 32°F
last April 29, first October 22
Median at 28°F
last April 12, first November 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 9Jun 1May 26May 18May 13May 9May 4Apr 30Apr 25
32°FMay 30May 15May 8May 2Apr 29Apr 25Apr 21Apr 17Apr 10
28°FMay 13May 1Apr 21Apr 17Apr 12Apr 9Apr 4Mar 31Mar 21
24°FApr 19Apr 9Apr 3Mar 30Mar 26Mar 17Mar 11Mar 6Feb 28
20°FMar 31Mar 20Mar 11Mar 6Feb 28Feb 25Feb 20Feb 15Feb 7
16°FMar 6Feb 27Feb 21Feb 17Feb 13Feb 9Feb 4Jan 31Jan 17

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 27Oct 1Oct 5Oct 8Oct 11Oct 14Oct 17Oct 21Oct 27
32°FOct 6Oct 12Oct 16Oct 19Oct 22Oct 26Oct 29Nov 2Nov 7
28°FOct 17Oct 21Oct 25Oct 29Nov 1Nov 4Nov 8Nov 13Nov 18
24°FOct 24Oct 30Nov 4Nov 7Nov 12Nov 16Nov 19Nov 24Nov 28
20°FNov 2Nov 9Nov 14Nov 18Nov 22Nov 25Nov 29Dec 3Dec 8
16°FNov 12Nov 19Nov 25Nov 28Dec 2Dec 7Dec 11Dec 15Dec 22

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°F175166161155151145138131122
32°F200190185179174169163156143
28°F231220212207201196189180168
24°F262253245239233226219210199
20°F290281275269263258251241230
16°F323311303296289284278271261

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
5,509
Cooling degree days, base 65°F
1,223
Growing degree days, base 40°F
5,821
Growing degree days, base 45°F
4,600
Growing degree days, base 50°F
3,539
Growing degree days, base 55°F
2,627
Growing degree days, base 60°F
1,862

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,07101
February82503
March650036
April4525109
May21945313
June52190589
July2438902
August3383845
September71147531
October36114185
November741024
December1,06302

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 9.9 km from Midvale. 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 USC00421759 (Cottonwood Weir). Public domain.