Alderson climate

Alderson Frost Dates and Growing Season

NOAA 1991-2020 normals for Alderson, 1.4 km from Alderson, elevation 1552 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Alderson. 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 26 and the first fall freeze around October 17, a growing season of about 173 days.

Median at 36°F
last May 8, first October 8
Median at 32°F
last April 26, first October 17
Median at 28°F
last April 12, first October 26

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 23May 18May 15May 11May 8May 4Apr 30Apr 27Apr 22
32°FMay 15May 9May 4Apr 30Apr 26Apr 23Apr 19Apr 16Apr 11
28°FMay 2Apr 22Apr 18Apr 14Apr 12Apr 8Apr 5Apr 2Mar 30
24°FApr 12Apr 7Apr 4Apr 1Mar 30Mar 27Mar 23Mar 19Mar 14
20°FApr 1Mar 28Mar 24Mar 21Mar 18Mar 15Mar 11Mar 6Feb 28
16°FMar 24Mar 18Mar 14Mar 10Mar 6Mar 2Feb 27Feb 20Feb 11

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 26Sep 30Oct 3Oct 5Oct 8Oct 11Oct 13Oct 16Oct 20
32°FOct 5Oct 9Oct 12Oct 14Oct 17Oct 19Oct 22Oct 25Oct 30
28°FOct 13Oct 17Oct 21Oct 23Oct 26Oct 28Oct 31Nov 3Nov 7
24°FOct 22Oct 27Oct 31Nov 2Nov 5Nov 7Nov 11Nov 14Nov 19
20°FNov 1Nov 5Nov 9Nov 12Nov 16Nov 20Nov 24Nov 29Dec 5
16°FNov 10Nov 17Nov 21Nov 26Dec 1Dec 4Dec 8Dec 14Dec 23

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°F173167162158154150146140133
32°F194187182177173169165159153
28°F217210205200196192188183173
24°F241234228223219215212207198
20°F267259252248242238233227220
16°F301291284277272265259252244

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
5,173
Cooling degree days, base 65°F
773
Growing degree days, base 40°F
5,603
Growing degree days, base 45°F
4,343
Growing degree days, base 50°F
3,238
Growing degree days, base 55°F
2,273
Growing degree days, base 60°F
1,451

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,04102
February85006
March719037
April3754155
May15349371
June20148578
July3252714
August5217677
September6792476
October34311187
November663028
December93506

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 1.4 km from Alderson. 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 USC00460102 (Alderson). Public domain.