Valley climate

Valley Frost Dates and Growing Season

NOAA 1991-2020 normals for Valley NWS, 1.9 km from Valley, elevation 1145 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Valley NWS. 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 15 and the first fall freeze around October 21, a growing season of about 187 days.

Median at 36°F
last April 25, first October 12
Median at 32°F
last April 15, first October 21
Median at 28°F
last April 5, first October 31

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 7May 3May 1Apr 28Apr 25Apr 23Apr 19Apr 16Apr 12
32°FApr 29Apr 24Apr 21Apr 17Apr 15Apr 12Apr 9Apr 6Apr 2
28°FApr 20Apr 15Apr 11Apr 8Apr 5Apr 3Apr 1Mar 28Mar 22
24°FApr 10Apr 6Apr 2Mar 31Mar 28Mar 25Mar 20Mar 17Mar 11
20°FApr 2Mar 30Mar 25Mar 21Mar 17Mar 15Mar 11Mar 8Mar 3
16°FMar 26Mar 18Mar 16Mar 13Mar 10Mar 7Mar 4Mar 1Feb 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°FSep 27Oct 1Oct 5Oct 9Oct 12Oct 14Oct 17Oct 20Oct 24
32°FOct 6Oct 12Oct 15Oct 18Oct 21Oct 24Oct 26Oct 29Nov 2
28°FOct 17Oct 21Oct 25Oct 28Oct 31Nov 2Nov 5Nov 8Nov 13
24°FOct 25Oct 31Nov 3Nov 5Nov 8Nov 11Nov 15Nov 19Nov 25
20°FNov 1Nov 7Nov 11Nov 15Nov 18Nov 21Nov 25Nov 29Dec 5
16°FNov 10Nov 16Nov 20Nov 23Nov 26Nov 30Dec 3Dec 7Dec 13

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°F187180176172168163160155148
32°F206201195191187182178174167
28°F228220215211207203199195187
24°F248240235231226221217212205
20°F267259254248243239235229220
16°F283276271266261257252247237

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
5,941
Cooling degree days, base 65°F
1,203
Growing degree days, base 40°F
5,910
Growing degree days, base 45°F
4,722
Growing degree days, base 50°F
3,660
Growing degree days, base 55°F
2,716
Growing degree days, base 60°F
1,894

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,26800
February1,03003
March772141
April41010146
May14381409
June13266703
July1382846
August4307769
September75136513
October35620199
November743030
December1,12801

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 1.9 km from Valley. 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 USC00258795 (Valley NWS). Public domain.