Douglas County climate

Douglas County Frost Dates and Growing Season

NOAA 1991-2020 normals for Pattison Ranger Staion, 18.7 km from Douglas County, elevation 1100 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Pattison Ranger Staion. 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 18 and the first fall freeze around October 3, a growing season of about 135 days.

Median at 36°F
last May 31, first September 24
Median at 32°F
last May 18, first October 3
Median at 28°F
last May 5, first October 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°FJun 13Jun 8Jun 5Jun 2May 31May 29May 26May 23May 18
32°FJun 3May 29May 25May 22May 18May 15May 13May 9May 4
28°FMay 21May 15May 11May 8May 5May 2Apr 30Apr 28Apr 22
24°FMay 8May 3Apr 30Apr 27Apr 25Apr 22Apr 19Apr 14Apr 10
20°FApr 27Apr 22Apr 18Apr 15Apr 12Apr 9Apr 6Apr 3Mar 31
16°FApr 18Apr 13Apr 9Apr 6Apr 4Apr 2Mar 31Mar 28Mar 21

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 10Sep 15Sep 19Sep 21Sep 24Sep 26Sep 29Oct 2Oct 6
32°FSep 20Sep 25Sep 28Sep 30Oct 3Oct 5Oct 8Oct 11Oct 16
28°FSep 30Oct 5Oct 8Oct 11Oct 14Oct 17Oct 20Oct 24Oct 30
24°FOct 11Oct 15Oct 19Oct 23Oct 27Oct 30Nov 1Nov 5Nov 10
20°FOct 22Oct 28Nov 1Nov 3Nov 5Nov 8Nov 11Nov 14Nov 19
16°FNov 1Nov 4Nov 7Nov 10Nov 13Nov 16Nov 18Nov 22Nov 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°F13212612111811411010610296
32°F156149144140135131127121116
28°F180173168164160156152147139
24°F203197193188184180175170163
20°F223218213209205201197192185
16°F238232227224220217213209203

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
9,091
Cooling degree days, base 65°F
287
Growing degree days, base 40°F
3,513
Growing degree days, base 45°F
2,598
Growing degree days, base 50°F
1,821
Growing degree days, base 55°F
1,173
Growing degree days, base 60°F
654

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,67800
February1,38900
March1,18102
April783014
May4565108
June17137325
July47125542
August5096511
September22823263
October612153
November1,02502
December1,47100

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 18.7 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 USC00476413 (Pattison Ranger Staion). Public domain.