Durham climate

Durham Frost Dates and Growing Season

NOAA 1991-2020 normals for Durham, 7.9 km from Durham, elevation 400 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Durham. 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 2 and the first fall freeze around November 4, a growing season of about 217 days.

Median at 36°F
last April 14, first October 27
Median at 32°F
last April 2, first November 4
Median at 28°F
last March 19, first November 16

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 1Apr 25Apr 21Apr 17Apr 14Apr 11Apr 8Apr 3Mar 30
32°FApr 18Apr 13Apr 9Apr 4Apr 2Mar 30Mar 26Mar 21Mar 15
28°FApr 6Apr 1Mar 27Mar 23Mar 19Mar 16Mar 11Mar 6Feb 28
24°FMar 24Mar 17Mar 12Mar 8Mar 4Mar 1Feb 25Feb 20Feb 11
20°FMar 13Mar 6Feb 28Feb 24Feb 17Feb 12Feb 6Feb 1Jan 23
16°FFeb 28Feb 19Feb 11Feb 5Feb 1Jan 28Jan 23Jan 16Jan 6

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 13Oct 19Oct 22Oct 25Oct 27Oct 30Nov 1Nov 2Nov 6
32°FOct 24Oct 28Nov 1Nov 2Nov 4Nov 6Nov 9Nov 13Nov 19
28°FNov 2Nov 5Nov 9Nov 12Nov 16Nov 20Nov 24Nov 30Dec 7
24°FNov 12Nov 18Nov 22Nov 27Dec 1Dec 5Dec 10Dec 21Jan 1
20°FNov 25Dec 2Dec 7Dec 14Dec 23Dec 29Jan 4Jan 9Jan 19
16°FDec 9Dec 21Dec 29Jan 1Jan 7Jan 11Jan 16Jan 23Feb 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°F214207203199194190185180172
32°F239231226221217213208204197
28°F269259252247242238233226219
24°F302293284277272265259252245
20°F334325317308302297290282272
16°F365356346338333328320310301

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
99% of years
16°F or colder
86% 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
3,750
Cooling degree days, base 65°F
1,350
Growing degree days, base 40°F
7,058
Growing degree days, base 45°F
5,580
Growing degree days, base 50°F
4,272
Growing degree days, base 55°F
3,135
Growing degree days, base 60°F
2,162

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January825012
February661019
March501399
April23529267
May74105497
June7269712
July0400865
August0338803
September25178603
October21925287
November495281
December709027

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 7.9 km from Durham. 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 USC00312515 (Durham). Public domain.