Wallace climate

Wallace Frost Dates and Growing Season

NOAA 1991-2020 normals for Milton Exp Stn, 12 km from Wallace, elevation 217 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Milton Exp Stn. 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 March 15 and the first fall freeze around November 13, a growing season of about 241 days.

Median at 36°F
last March 30, first November 3
Median at 32°F
last March 15, first November 13
Median at 28°F
last March 1, first November 24

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°FApr 16Apr 9Apr 5Apr 2Mar 30Mar 26Mar 22Mar 17Mar 10
32°FApr 3Mar 28Mar 24Mar 19Mar 15Mar 11Mar 7Mar 1Feb 22
28°FMar 22Mar 15Mar 10Mar 6Mar 1Feb 26Feb 20Feb 14Feb 4
24°FMar 12Mar 3Feb 27Feb 21Feb 14Feb 6Feb 1Jan 26Jan 15
20°FMar 1Feb 17Feb 8Feb 2Jan 30Jan 24Jan 17Jan 10Dec 28
16°FFeb 9Feb 2Jan 31Jan 25Jan 20Jan 16Jan 11Jan 3Dec 28

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 21Oct 25Oct 28Nov 1Nov 3Nov 5Nov 8Nov 12Nov 17
32°FOct 30Nov 2Nov 5Nov 9Nov 13Nov 16Nov 20Nov 24Dec 2
28°FNov 5Nov 10Nov 16Nov 20Nov 24Nov 28Dec 3Dec 9Dec 20
24°FNov 17Nov 25Dec 1Dec 6Dec 12Dec 21Dec 29Jan 6Jan 18
20°FDec 3Dec 12Dec 21Dec 30Jan 3Jan 8Jan 15Jan 22Feb 4
16°FDec 14Dec 28Jan 1Jan 6Jan 10Jan 15Jan 18Jan 25Feb 4

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°F243234228223218213207203196
32°F269260253246241236231225217
28°F307293284276270264258251242
24°F345330320311304296288280266
20°F365365355345336330321310299
16°F365365365365365362351338331

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
97% of years
20°F or colder
79% of years
16°F or colder
42% 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
2,029
Cooling degree days, base 65°F
2,147
Growing degree days, base 40°F
9,305
Growing degree days, base 45°F
7,589
Growing degree days, base 50°F
5,987
Growing degree days, base 55°F
4,536
Growing degree days, base 60°F
3,248

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January526294
February3695128
March22920278
April9373433
May10235690
June0400850
July0467932
August0456921
September1333781
October73130525
November28022231
December4495125

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 12 km from Wallace. 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 USC00085793 (Milton Exp Stn). Public domain.