Clarkston climate

Clarkston Frost Dates and Growing Season

NOAA 1991-2020 normals for Cutler Dam, 9.7 km from Clarkston, elevation 4290 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cutler Dam. 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 12, a growing season of about 160 days.

Median at 36°F
last May 19, first October 1
Median at 32°F
last May 3, first October 12
Median at 28°F
last April 19, first October 24

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 10Jun 3May 29May 23May 19May 16May 11May 6May 2
32°FMay 24May 17May 11May 6May 3Apr 30Apr 27Apr 22Apr 17
28°FMay 8May 2Apr 28Apr 24Apr 19Apr 14Apr 10Apr 4Mar 29
24°FApr 24Apr 14Apr 9Apr 3Mar 31Mar 25Mar 18Mar 13Mar 8
20°FApr 2Mar 25Mar 17Mar 13Mar 10Mar 7Mar 4Mar 1Feb 26
16°FMar 15Mar 10Mar 7Mar 3Mar 1Feb 27Feb 23Feb 19Feb 12

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 12Sep 21Sep 24Sep 27Oct 1Oct 3Oct 6Oct 9Oct 14
32°FSep 27Oct 1Oct 5Oct 8Oct 12Oct 15Oct 18Oct 22Oct 26
28°FOct 8Oct 14Oct 18Oct 21Oct 24Oct 27Oct 31Nov 3Nov 9
24°FOct 20Oct 25Oct 29Nov 1Nov 5Nov 8Nov 12Nov 17Nov 22
20°FOct 27Nov 3Nov 8Nov 12Nov 17Nov 21Nov 23Nov 26Dec 1
16°FNov 5Nov 13Nov 19Nov 23Nov 26Nov 29Dec 1Dec 6Dec 12

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°F155148143137132126121113105
32°F181174169164160155149143132
28°F212203197192187182178172162
24°F242234227220215209202195185
20°F269261256250245240233226216
16°F291282276272267263258252243

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
6,604
Cooling degree days, base 65°F
742
Growing degree days, base 40°F
4,804
Growing degree days, base 45°F
3,700
Growing degree days, base 50°F
2,748
Growing degree days, base 55°F
1,951
Growing degree days, base 60°F
1,285

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,26500
February1,00900
March777010
April528058
May27819236
June83102472
July7302761
August9258715
September12259396
October470298
November83704
December1,22100

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 9.7 km from Clarkston. 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 USC00421918 (Cutler Dam). Public domain.