Douglas County climate

Douglas County Frost Dates and Growing Season

NOAA 1991-2020 normals for Armour, 8.3 km from Douglas County, elevation 1510 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Armour. 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 3 and the first fall freeze around October 6, a growing season of about 157 days.

Median at 36°F
last May 12, first September 28
Median at 32°F
last May 3, first October 6
Median at 28°F
last April 21, first October 16

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 26May 21May 18May 15May 12May 9May 7May 3Apr 30
32°FMay 18May 12May 9May 5May 3Apr 30Apr 27Apr 23Apr 17
28°FMay 7May 2Apr 28Apr 24Apr 21Apr 17Apr 15Apr 10Apr 6
24°FApr 26Apr 21Apr 17Apr 14Apr 11Apr 7Apr 5Apr 2Mar 28
20°FApr 17Apr 11Apr 7Apr 4Apr 1Mar 30Mar 27Mar 22Mar 15
16°FApr 7Apr 3Mar 31Mar 28Mar 24Mar 20Mar 16Mar 12Mar 8

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

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°F156150146143139135131127121
32°F176169164160157153148144138
28°F197190185180176173168163156
24°F218211206201198193187183175
20°F237229224220216212208203196
16°F254247241237232228223218211

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
6,747
Cooling degree days, base 65°F
929
Growing degree days, base 40°F
5,269
Growing degree days, base 45°F
4,156
Growing degree days, base 50°F
3,160
Growing degree days, base 55°F
2,290
Growing degree days, base 60°F
1,542

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,36700
February1,10001
March870021
April4936102
May20840315
June31182601
July5316776
August9265721
September101111465
October4429141
November867016
December1,25500

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 8.3 km from Douglas County. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00390296 (Armour). Public domain.