Walnut Grove climate

Walnut Grove Frost Dates and Growing Season

NOAA 1991-2020 normals for Ash Grove 4S, 17 km from Walnut Grove, elevation 1129 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ash Grove 4S. 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 11 and the first fall freeze around October 24, a growing season of about 196 days.

Median at 36°F
last April 22, first October 16
Median at 32°F
last April 11, first October 24
Median at 28°F
last March 31, first November 2

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

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 6Oct 10Oct 13Oct 16Oct 18Oct 20Oct 23Oct 27
32°FOct 13Oct 17Oct 19Oct 22Oct 24Oct 26Oct 29Nov 1Nov 5
28°FOct 19Oct 24Oct 28Oct 31Nov 2Nov 5Nov 8Nov 12Nov 18
24°FOct 30Nov 3Nov 6Nov 9Nov 13Nov 16Nov 21Nov 27Dec 2
20°FNov 6Nov 12Nov 17Nov 21Nov 25Nov 30Dec 4Dec 9Dec 16
16°FNov 17Nov 25Nov 30Dec 4Dec 9Dec 14Dec 19Dec 24Jan 1

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°F194187182178174170166162155
32°F217210204199196192188183176
28°F240232226221217213208203196
24°F266256250245238233228223213
20°F287279274268263257251244234
16°F315305299292286280274267257

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
4,345
Cooling degree days, base 65°F
1,556
Growing degree days, base 40°F
7,018
Growing degree days, base 45°F
5,635
Growing degree days, base 50°F
4,402
Growing degree days, base 55°F
3,318
Growing degree days, base 60°F
2,372

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January96809
February759026
March560696
April27628247
May88127507
June4305751
July0442907
August1404868
September37200614
October25041288
November553374
December849015

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 17 km from Walnut Grove. 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 USC00230304 (Ash Grove 4S). Public domain.