Erwin climate

Erwin Frost Dates and Growing Season

NOAA 1991-2020 normals for Erwin 1 W, 0.9 km from Erwin, elevation 1720 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Erwin 1 W. 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 21 and the first fall freeze around October 23, a growing season of about 183 days.

Median at 36°F
last May 3, first October 14
Median at 32°F
last April 21, first October 23
Median at 28°F
last April 7, 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°FMay 20May 13May 10May 7May 3Apr 30Apr 27Apr 23Apr 18
32°FMay 11May 5Apr 30Apr 25Apr 21Apr 18Apr 15Apr 10Apr 4
28°FApr 30Apr 21Apr 16Apr 11Apr 7Apr 4Mar 31Mar 28Mar 20
24°FApr 12Apr 6Apr 2Mar 30Mar 26Mar 22Mar 18Mar 14Mar 6
20°FMar 31Mar 26Mar 21Mar 16Mar 12Mar 7Mar 2Feb 26Feb 17
16°FMar 21Mar 13Mar 7Mar 2Feb 26Feb 19Feb 12Feb 5Jan 29

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 3Oct 7Oct 10Oct 12Oct 14Oct 16Oct 20Oct 23Oct 27
32°FOct 11Oct 14Oct 17Oct 21Oct 23Oct 25Oct 28Nov 1Nov 4
28°FOct 18Oct 23Oct 26Oct 29Nov 1Nov 2Nov 5Nov 8Nov 13
24°FOct 28Nov 1Nov 4Nov 6Nov 9Nov 13Nov 17Nov 21Nov 27
20°FNov 7Nov 12Nov 16Nov 21Nov 25Nov 29Dec 1Dec 7Dec 14
16°FNov 18Nov 25Dec 1Dec 4Dec 9Dec 15Dec 23Dec 30Jan 5

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°F182175171167163159154149141
32°F203197192187183178174167160
28°F229220214210205200196190180
24°F254246239234229223218213206
20°F288277269261256249244238228
16°F321309302296290281275266254

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
4,390
Cooling degree days, base 65°F
908
Growing degree days, base 40°F
6,219
Growing degree days, base 45°F
4,830
Growing degree days, base 50°F
3,607
Growing degree days, base 55°F
2,550
Growing degree days, base 60°F
1,652

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January902012
February732016
March595166
April3239190
May12159409
June14177613
July1273738
August1249713
September43121529
October27717240
November580159
December801021

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 0.9 km from Erwin. 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 USC00402934 (Erwin 1 W). Public domain.