Douglas climate

Douglas Frost Dates and Growing Season

NOAA 1991-2020 normals for Douglas, 3.6 km from Douglas, elevation 233 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Douglas. 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 5 and the first fall freeze around November 26, a growing season of about 267 days.

Median at 36°F
last March 19, first November 12
Median at 32°F
last March 5, first November 26
Median at 28°F
last February 15, first December 14

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 4Mar 31Mar 26Mar 22Mar 19Mar 15Mar 10Mar 6Feb 28
32°FMar 24Mar 18Mar 13Mar 9Mar 5Feb 28Feb 25Feb 18Feb 8
28°FMar 12Mar 5Feb 28Feb 21Feb 15Feb 7Feb 1Jan 27Jan 14
24°FMar 1Feb 18Feb 8Feb 1Jan 30Jan 23Jan 16Jan 9Dec 30
20°FFeb 16Feb 7Feb 1Jan 28Jan 21Jan 14Jan 10Jan 4Dec 30
16°FFeb 11Feb 4Feb 1Jan 27Jan 21Jan 18Jan 15Jan 12Jan 6

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 2Nov 5Nov 8Nov 12Nov 16Nov 19Nov 24Dec 1
32°FNov 6Nov 13Nov 18Nov 22Nov 26Nov 30Dec 4Dec 10Dec 23
28°FNov 20Nov 27Dec 2Dec 7Dec 14Dec 22Dec 31Jan 6Jan 17
24°FDec 2Dec 12Dec 22Dec 30Jan 2Jan 8Jan 14Jan 25Feb 4
20°FDec 19Dec 30Jan 2Jan 7Jan 12Jan 17Jan 26Feb 1Feb 10
16°FJan 4Jan 10Jan 14Jan 15Jan 19Jan 23Jan 29Feb 2Feb 8

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°F268258252246241237231224216
32°F299288281273267261255248239
28°F340327317308302294287278267
24°F365363351342334327320310300
20°F365365365365365363350337325
16°F365365365365365365365365356

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
99% of years
24°F or colder
80% of years
20°F or colder
43% of years
16°F or colder
12% 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
1,862
Cooling degree days, base 65°F
2,411
Growing degree days, base 40°F
9,716
Growing degree days, base 45°F
7,981
Growing degree days, base 50°F
6,352
Growing degree days, base 55°F
4,870
Growing degree days, base 60°F
3,551

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January4895108
February3507142
March21331303
April7397476
May9283739
June0441891
July0522987
August0502967
September2351799
October61139544
November24925252
December4168143

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 3.6 km from Douglas. 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 USC00092783 (Douglas). Public domain.