Westbrook climate

Westbrook Frost Dates and Growing Season

NOAA 1991-2020 normals for Lamberton Sw Rsch & Outreach C, 24 km from Westbrook, elevation 1140 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lamberton Sw Rsch & Outreach C. 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 2, a growing season of about 152 days.

Median at 36°F
last May 11, first September 25
Median at 32°F
last May 3, first October 2
Median at 28°F
last April 24, first October 13

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 24May 19May 16May 13May 11May 9May 7May 4Apr 30
32°FMay 15May 11May 8May 5May 3May 1Apr 29Apr 25Apr 19
28°FMay 7May 2Apr 30Apr 27Apr 24Apr 21Apr 18Apr 14Apr 8
24°FApr 29Apr 24Apr 21Apr 18Apr 14Apr 11Apr 8Apr 5Mar 31
20°FApr 22Apr 17Apr 12Apr 9Apr 7Apr 4Mar 31Mar 26Mar 19
16°FApr 15Apr 9Apr 4Mar 31Mar 29Mar 24Mar 20Mar 16Mar 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 10Sep 15Sep 19Sep 22Sep 25Sep 27Oct 1Oct 3Oct 6
32°FSep 18Sep 24Sep 27Sep 30Oct 2Oct 5Oct 8Oct 11Oct 16
28°FSep 29Oct 3Oct 7Oct 11Oct 13Oct 16Oct 19Oct 22Oct 26
24°FOct 9Oct 14Oct 18Oct 21Oct 23Oct 26Oct 29Nov 1Nov 6
20°FOct 19Oct 24Oct 27Oct 30Nov 1Nov 4Nov 7Nov 9Nov 14
16°FOct 28Nov 1Nov 4Nov 7Nov 10Nov 12Nov 15Nov 19Nov 24

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°F154147142139136132128122116
32°F171165159155152149146141134
28°F192185180175171168164159153
24°F214205200195191188184178172
20°F230222217212209205201195188
16°F246239234230225220216210203

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
8,080
Cooling degree days, base 65°F
616
Growing degree days, base 40°F
4,490
Growing degree days, base 45°F
3,485
Growing degree days, base 50°F
2,589
Growing degree days, base 55°F
1,809
Growing degree days, base 60°F
1,147

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,58700
February1,31600
March1,07609
April632258
May27238267
June47146549
July12217669
August30148583
September17260351
October552694
November977010
December1,40700

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 24 km from Westbrook. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00214546 (Lamberton Sw Rsch & Outreach C). Public domain.