Dexter climate

Dexter Frost Dates and Growing Season

NOAA 1991-2020 normals for Chelsea, 10.3 km from Dexter, elevation 900 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Chelsea. 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 30 and the first fall freeze around October 12, a growing season of about 163 days.

Median at 36°F
last May 11, first September 30
Median at 32°F
last April 30, first October 12
Median at 28°F
last April 20, first October 26

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 27May 22May 18May 14May 11May 8May 4May 1Apr 26
32°FMay 17May 11May 7May 4Apr 30Apr 28Apr 25Apr 21Apr 18
28°FMay 6Apr 30Apr 27Apr 23Apr 20Apr 17Apr 15Apr 11Apr 6
24°FApr 24Apr 18Apr 14Apr 11Apr 7Apr 5Apr 2Mar 31Mar 26
20°FApr 13Apr 6Apr 3Mar 31Mar 29Mar 26Mar 23Mar 19Mar 14
16°FApr 1Mar 28Mar 25Mar 22Mar 19Mar 16Mar 14Mar 10Mar 4

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 28Sep 30Oct 3Oct 5Oct 9Oct 13
32°FSep 28Oct 2Oct 5Oct 8Oct 12Oct 16Oct 19Oct 22Oct 27
28°FOct 10Oct 16Oct 20Oct 23Oct 26Oct 29Nov 1Nov 4Nov 9
24°FOct 23Oct 29Nov 1Nov 3Nov 6Nov 8Nov 12Nov 15Nov 21
20°FNov 4Nov 8Nov 11Nov 14Nov 17Nov 21Nov 25Nov 28Dec 4
16°FNov 13Nov 18Nov 22Nov 26Nov 29Dec 2Dec 5Dec 12Dec 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°F161155149145142137133128120
32°F184177171168163159154148140
28°F209201196191187182177172165
24°F231225220215212208203198191
20°F256248242238234229226220213
16°F278271264259254250246240233

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
6,655
Cooling degree days, base 65°F
610
Growing degree days, base 40°F
4,764
Growing degree days, base 45°F
3,669
Growing degree days, base 50°F
2,705
Growing degree days, base 55°F
1,870
Growing degree days, base 60°F
1,165

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,28600
February1,10001
March935114
April543580
May23636287
June47127530
July12211665
August19164609
September13460382
October4537120
November780017
December1,10801

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 10.3 km from Dexter. 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 USC00201502 (Chelsea). Public domain.