Carleton climate

Carleton Frost Dates and Growing Season

NOAA 1991-2020 normals for Carleton 2W, 3.7 km from Carleton, elevation 627 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Carleton 2W. 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 April 27 and the first fall freeze around October 20, a growing season of about 176 days.

Median at 36°F
last May 6, first October 6
Median at 32°F
last April 27, first October 20
Median at 28°F
last April 15, first November 1

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 22May 17May 13May 9May 6May 3Apr 30Apr 28Apr 22
32°FMay 13May 6May 2Apr 30Apr 27Apr 23Apr 20Apr 17Apr 12
28°FMay 2Apr 25Apr 21Apr 17Apr 15Apr 12Apr 8Apr 4Mar 31
24°FApr 16Apr 11Apr 7Apr 3Apr 2Mar 31Mar 27Mar 22Mar 18
20°FApr 6Apr 1Mar 29Mar 26Mar 22Mar 19Mar 16Mar 12Mar 8
16°FMar 28Mar 22Mar 18Mar 16Mar 13Mar 10Mar 7Mar 3Feb 26

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 23Sep 27Sep 30Oct 3Oct 6Oct 8Oct 12Oct 16Oct 21
32°FOct 4Oct 9Oct 13Oct 17Oct 20Oct 23Oct 26Oct 29Nov 2
28°FOct 17Oct 23Oct 26Oct 30Nov 1Nov 2Nov 5Nov 9Nov 14
24°FOct 30Nov 2Nov 5Nov 8Nov 11Nov 14Nov 17Nov 21Nov 26
20°FNov 7Nov 12Nov 16Nov 19Nov 23Nov 26Nov 30Dec 5Dec 12
16°FNov 17Nov 23Nov 28Dec 1Dec 4Dec 8Dec 13Dec 18Dec 23

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°F174167162158153150145141134
32°F195189184179176172167161154
28°F220213208203199195191186180
24°F244236230226223219214209203
20°F268260254250246241236230223
16°F290282276271266262258252245

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
6,302
Cooling degree days, base 65°F
699
Growing degree days, base 40°F
5,029
Growing degree days, base 45°F
3,887
Growing degree days, base 50°F
2,889
Growing degree days, base 55°F
2,030
Growing degree days, base 60°F
1,292

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,24601
February1,07500
March890015
April514273
May21335304
June28146569
July7244702
August11192646
September10872415
October4038142
November741020
December1,06602

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 3.7 km from Carleton. 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 USC00201250 (Carleton 2W). Public domain.