Douglas County climate

Douglas County Frost Dates and Growing Season

NOAA 1991-2020 normals for Alexandria Muni AP, 8.7 km from Douglas County, elevation 1416 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Alexandria Muni AP. 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 2 and the first fall freeze around October 8, a growing season of about 159 days.

Median at 36°F
last May 11, first September 30
Median at 32°F
last May 2, first October 8
Median at 28°F
last April 21, first October 19

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 27May 22May 17May 14May 11May 8May 6May 3Apr 30
32°FMay 15May 10May 7May 4May 2Apr 30Apr 27Apr 23Apr 18
28°FMay 4Apr 30Apr 27Apr 24Apr 21Apr 19Apr 16Apr 12Apr 8
24°FApr 26Apr 22Apr 18Apr 16Apr 13Apr 11Apr 8Apr 5Apr 2
20°FApr 20Apr 16Apr 12Apr 9Apr 6Apr 4Apr 2Mar 30Mar 23
16°FApr 14Apr 8Apr 5Apr 2Apr 1Mar 29Mar 24Mar 20Mar 14

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 18Sep 22Sep 25Sep 27Sep 30Oct 2Oct 4Oct 7Oct 12
32°FSep 27Sep 30Oct 3Oct 5Oct 8Oct 10Oct 14Oct 17Oct 20
28°FOct 5Oct 9Oct 13Oct 16Oct 19Oct 21Oct 24Oct 27Oct 31
24°FOct 14Oct 20Oct 23Oct 26Oct 29Oct 31Nov 2Nov 5Nov 10
20°FOct 24Oct 29Oct 31Nov 3Nov 5Nov 7Nov 10Nov 13Nov 18
16°FOct 31Nov 4Nov 7Nov 10Nov 12Nov 15Nov 18Nov 21Nov 25

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°F157151147143140136132127121
32°F177171165162159156151147140
28°F199191186182178174169165159
24°F217210206202198193189185177
20°F230224220216212209204200193
16°F247239234230226222217213207

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
8,653
Cooling degree days, base 65°F
495
Growing degree days, base 40°F
4,169
Growing degree days, base 45°F
3,205
Growing degree days, base 50°F
2,347
Growing degree days, base 55°F
1,603
Growing degree days, base 60°F
981

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,68500
February1,40400
March1,14704
April674139
May30624225
June6899482
July16188637
August30138573
September19343314
October599368
November1,04105
December1,49100

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 8.7 km from Douglas County. 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 USW00014910 (Alexandria Muni AP). Public domain.