Hampstead climate

Hampstead Frost Dates and Growing Season

NOAA 1991-2020 normals for Wilmington 7 N, 20 km from Hampstead, elevation 40 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Wilmington 7 N. 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 March 29 and the first fall freeze around November 8, a growing season of about 226 days.

Median at 36°F
last April 8, first October 30
Median at 32°F
last March 29, first November 8
Median at 28°F
last March 16, first November 20

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°FApr 22Apr 17Apr 13Apr 10Apr 8Apr 5Apr 2Mar 31Mar 25
32°FApr 11Apr 6Apr 3Mar 31Mar 29Mar 25Mar 21Mar 17Mar 12
28°FApr 1Mar 27Mar 23Mar 19Mar 16Mar 13Mar 9Mar 4Feb 26
24°FMar 22Mar 16Mar 11Mar 6Mar 2Feb 26Feb 20Feb 12Feb 2
20°FMar 10Mar 1Feb 24Feb 15Feb 7Feb 1Jan 28Jan 20Jan 9
16°FFeb 24Feb 10Feb 1Jan 29Jan 24Jan 18Jan 13Jan 6Dec 29

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°FOct 17Oct 22Oct 25Oct 27Oct 30Nov 1Nov 4Nov 7Nov 11
32°FOct 27Oct 31Nov 3Nov 5Nov 8Nov 11Nov 14Nov 19Nov 26
28°FNov 4Nov 8Nov 12Nov 16Nov 20Nov 24Nov 29Dec 2Dec 8
24°FNov 14Nov 21Nov 25Dec 1Dec 3Dec 6Dec 14Dec 23Jan 3
20°FNov 30Dec 4Dec 10Dec 16Dec 24Dec 31Jan 5Jan 14Jan 25
16°FDec 12Dec 19Dec 27Jan 1Jan 7Jan 12Jan 17Jan 25Feb 2

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°F224217213209206202198193187
32°F249240235230226222217213206
28°F279269262254249245240234227
24°F314302293284278271265259248
20°F351337329321314306301291278
16°F365365365356348339333321308

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
95% of years
16°F or colder
71% 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
2,748
Cooling degree days, base 65°F
1,816
Growing degree days, base 40°F
8,340
Growing degree days, base 45°F
6,720
Growing degree days, base 50°F
5,244
Growing degree days, base 55°F
3,930
Growing degree days, base 60°F
2,786

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January637158
February510267
March38310169
April15650352
May34168599
June2353801
July0468933
August0420885
September8262703
October12168418
November34312176
December554484

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 20 km from Hampstead. 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 USC00319467 (Wilmington 7 N). Public domain.