Harrison climate

Harrison Frost Dates and Growing Season

NOAA 1991-2020 normals for Bridgton 3 Nw, 7 km from Harrison, elevation 508 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Bridgton 3 Nw. 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 5 and the first fall freeze around October 5, a growing season of about 151 days.

Median at 36°F
last May 18, first September 27
Median at 32°F
last May 5, first October 5
Median at 28°F
last April 25, first October 19

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

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 16Sep 21Sep 24Sep 27Sep 30Oct 1Oct 4Oct 8
32°FSep 22Sep 26Oct 1Oct 2Oct 5Oct 7Oct 10Oct 15Oct 21
28°FOct 1Oct 7Oct 10Oct 15Oct 19Oct 22Oct 26Oct 29Nov 3
24°FOct 15Oct 22Oct 26Oct 30Nov 1Nov 4Nov 7Nov 10Nov 15
20°FOct 29Nov 3Nov 7Nov 11Nov 14Nov 17Nov 20Nov 23Nov 27
16°FNov 10Nov 15Nov 19Nov 22Nov 25Nov 28Dec 1Dec 2Dec 7

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°F147142138134131127123118111
32°F169163158155151147144140134
28°F193187183178175171167163156
24°F219213208204200197193187180
20°F242236231227224220216211205
16°F262255251246242238235230224

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
7,972
Cooling degree days, base 65°F
274
Growing degree days, base 40°F
3,764
Growing degree days, base 45°F
2,792
Growing degree days, base 50°F
1,946
Growing degree days, base 55°F
1,231
Growing degree days, base 60°F
662

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,46900
February1,26700
March1,10203
April694124
May3438169
June12146377
July31115549
August4882499
September21822266
October563155
November87205
December1,24500

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 7 km from Harrison. 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 USC00170844 (Bridgton 3 Nw). Public domain.