Cairnbrook climate

Cairnbrook Frost Dates and Growing Season

NOAA 1991-2020 normals for Shawnee SP, 18.1 km from Cairnbrook, elevation 1275 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Shawnee SP. 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 4 and the first fall freeze around October 10, a growing season of about 158 days.

Median at 36°F
last May 17, first October 1
Median at 32°F
last May 4, first October 10
Median at 28°F
last April 21, first October 22

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 30May 26May 23May 20May 17May 13May 9May 5Apr 30
32°FMay 21May 17May 12May 8May 4May 1Apr 28Apr 24Apr 19
28°FMay 12May 3Apr 29Apr 25Apr 21Apr 18Apr 14Apr 10Apr 5
24°FApr 24Apr 18Apr 14Apr 10Apr 7Apr 5Apr 3Mar 30Mar 24
20°FApr 10Apr 5Apr 2Mar 31Mar 28Mar 25Mar 21Mar 17Mar 12
16°FMar 31Mar 26Mar 21Mar 18Mar 16Mar 13Mar 10Mar 7Mar 2

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 28Oct 1Oct 3Oct 5Oct 9Oct 13
32°FSep 28Oct 2Oct 4Oct 7Oct 10Oct 12Oct 15Oct 19Oct 23
28°FOct 7Oct 12Oct 16Oct 20Oct 22Oct 25Oct 28Oct 31Nov 4
24°FOct 18Oct 24Oct 28Oct 31Nov 2Nov 5Nov 7Nov 11Nov 17
20°FNov 1Nov 5Nov 8Nov 12Nov 15Nov 18Nov 22Nov 26Dec 2
16°FNov 9Nov 14Nov 19Nov 23Nov 28Dec 1Dec 4Dec 10Dec 19

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°F155150145140136132128124118
32°F178171166162158154149145137
28°F203197191187182178172167160
24°F230222217213209204199192185
20°F256246241237232227222218212
16°F281272266260255250246241233

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
6,150
Cooling degree days, base 65°F
601
Growing degree days, base 40°F
4,897
Growing degree days, base 45°F
3,747
Growing degree days, base 50°F
2,743
Growing degree days, base 55°F
1,882
Growing degree days, base 60°F
1,164

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,16202
February99701
March870015
April4795107
May22435293
June55119515
July8208665
August19174620
September12856382
October4406119
November735019
December1,03505

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 18.1 km from Cairnbrook. 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 USC00368011 (Shawnee SP). Public domain.