Sunset climate

Sunset Frost Dates and Growing Season

NOAA 1991-2020 normals for Grand Coteau, 2.4 km from Sunset, elevation 55 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Grand Coteau. 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 February 28 and the first fall freeze around November 23, a growing season of about 267 days.

Median at 36°F
last March 18, first November 13
Median at 32°F
last February 28, first November 23
Median at 28°F
last February 6, first December 8

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 7Apr 3Mar 29Mar 23Mar 18Mar 13Mar 8Mar 3Feb 24
32°FMar 25Mar 16Mar 10Mar 4Feb 28Feb 24Feb 18Feb 10Jan 31
28°FMar 8Feb 28Feb 22Feb 14Feb 6Jan 31Jan 26Jan 18Jan 5
24°FFeb 26Feb 14Feb 3Jan 30Jan 24Jan 18Jan 11Jan 2Dec 22
20°FFeb 10Feb 1Jan 27Jan 21Jan 16Jan 10Jan 4Dec 29Dec 21
16°F–––––––––

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 30Nov 3Nov 5Nov 9Nov 13Nov 16Nov 20Nov 24Dec 1
32°FNov 5Nov 11Nov 16Nov 19Nov 23Nov 27Dec 2Dec 7Dec 16
28°FNov 14Nov 22Nov 28Dec 3Dec 8Dec 14Dec 24Jan 1Jan 11
24°FDec 2Dec 10Dec 18Dec 24Dec 30Jan 4Jan 9Jan 17Feb 1
20°FDec 17Dec 24Dec 31Jan 3Jan 7Jan 13Jan 19Jan 27Feb 3
16°F–––––––––

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°F266257250245239233227220212
32°F301289279273267261253247237
28°F339327317309302294287277265
24°F365365356345337332324313301
20°F365365365365365365358346333
16°F365365365365365365365365365

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
97% of years
24°F or colder
75% of years
20°F or colder
39% of years
16°F or colder
10% 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
1,467
Cooling degree days, base 65°F
2,698
Growing degree days, base 40°F
10,382
Growing degree days, base 45°F
8,617
Growing degree days, base 50°F
6,929
Growing degree days, base 55°F
5,363
Growing degree days, base 60°F
3,943

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January40112160
February27421205
March15060385
April44137543
May4314775
June0459909
July0530995
August0532997
September1391840
October40179606
November19743317
December35621197

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 2.4 km from Sunset. 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 USC00163800 (Grand Coteau). Public domain.