Holderness climate

Holderness Frost Dates and Growing Season

NOAA 1991-2020 normals for Plymouth, 7.6 km from Holderness, elevation 660 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Plymouth. 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 20 and the first fall freeze around September 27, a growing season of about 128 days.

Median at 36°F
last May 31, first September 15
Median at 32°F
last May 20, first September 27
Median at 28°F
last May 7, first October 6

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 13Jun 9Jun 5Jun 3May 31May 29May 26May 22May 17
32°FJun 4May 30May 26May 23May 20May 17May 14May 10May 6
28°FMay 24May 19May 14May 10May 7May 4May 1Apr 27Apr 22
24°FMay 9May 4Apr 30Apr 27Apr 23Apr 20Apr 17Apr 13Apr 7
20°FApr 25Apr 19Apr 14Apr 10Apr 7Apr 5Apr 3Apr 1Mar 27
16°FApr 11Apr 6Apr 4Apr 1Mar 31Mar 29Mar 25Mar 21Mar 17

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 1Sep 6Sep 9Sep 12Sep 15Sep 18Sep 21Sep 24Sep 28
32°FSep 14Sep 18Sep 21Sep 24Sep 27Sep 29Oct 1Oct 4Oct 7
28°FSep 24Sep 29Oct 1Oct 3Oct 6Oct 9Oct 12Oct 16Oct 22
24°FOct 3Oct 8Oct 12Oct 16Oct 19Oct 23Oct 28Nov 1Nov 6
20°FOct 17Oct 24Oct 28Nov 1Nov 3Nov 7Nov 10Nov 14Nov 19
16°FNov 2Nov 7Nov 12Nov 15Nov 18Nov 21Nov 24Nov 27Dec 1

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°F1241181141101071031009689
32°F147141136132128125121116110
28°F173165160155151147143137129
24°F201193187182178173168162155
20°F228222216211207202197192183
16°F251244239235230226221217208

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
8,072
Cooling degree days, base 65°F
242
Growing degree days, base 40°F
3,625
Growing degree days, base 45°F
2,664
Growing degree days, base 50°F
1,837
Growing degree days, base 55°F
1,148
Growing degree days, base 60°F
605

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,45400
February1,24200
March1,10101
April698123
May3715147
June13643359
July40104528
August6470471
September22319260
October590145
November89304
December1,26200

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 7.6 km from Holderness. 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 USC00276945 (Plymouth). Public domain.