Wallace climate

Wallace Frost Dates and Growing Season

NOAA 1991-2020 normals for Wallace, 0.3 km from Wallace, elevation 2710 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Wallace. 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 May 5 and the first fall freeze around October 2, a growing season of about 149 days.

Median at 36°F
last May 27, first September 19
Median at 32°F
last May 5, first October 2
Median at 28°F
last April 19, first October 18

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 14Jun 8Jun 2May 30May 27May 23May 19May 15May 10
32°FMay 21May 15May 11May 8May 5May 2Apr 30Apr 27Apr 22
28°FMay 2Apr 28Apr 25Apr 22Apr 19Apr 15Apr 10Apr 4Mar 30
24°FApr 14Apr 7Apr 3Mar 31Mar 27Mar 23Mar 18Mar 12Mar 7
20°FMar 29Mar 22Mar 17Mar 12Mar 9Mar 6Mar 3Feb 28Feb 20
16°FMar 14Mar 9Mar 6Mar 3Feb 28Feb 25Feb 19Feb 13Feb 2

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

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°F1361291231171131081039687
32°F170162158153149146141135127
28°F208200191186181176172166158
24°F250239231224219214208201191
20°F279270264257251244238232223
16°F310299291284277270264256243

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
7,144
Cooling degree days, base 65°F
238
Growing degree days, base 40°F
3,527
Growing degree days, base 45°F
2,532
Growing degree days, base 50°F
1,716
Growing degree days, base 55°F
1,061
Growing degree days, base 60°F
568

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,11100
February93900
March85901
April623027
May3784148
June20825277
July68102499
August7287482
September24519243
October608039
November90201
December1,13100

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 0.3 km from Wallace. 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 USC00109498 (Wallace). Public domain.