Hatteras climate

Hatteras Frost Dates and Growing Season

NOAA 1991-2020 normals for Cape Hatteras AP, 6.4 km from Hatteras, elevation 11 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cape Hatteras AP. 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 4 and the first fall freeze around December 22, a growing season of about 290 days.

Median at 36°F
last March 19, first December 2
Median at 32°F
last March 4, first December 22
Median at 28°F
last February 12, first January 8

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 4Mar 31Mar 27Mar 23Mar 19Mar 15Mar 11Mar 6Feb 28
32°FMar 25Mar 19Mar 13Mar 8Mar 4Feb 28Feb 23Feb 15Feb 4
28°FMar 11Mar 3Feb 26Feb 20Feb 12Feb 6Feb 1Jan 28Jan 17
24°FFeb 26Feb 19Feb 10Feb 5Jan 31Jan 28Jan 22Jan 16Jan 10
20°FFeb 15Feb 8Feb 3Jan 30Jan 28Jan 23Jan 18Jan 15Jan 11
16°F–––––––––

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°FNov 17Nov 22Nov 26Nov 29Dec 2Dec 6Dec 11Dec 17Dec 27
32°FNov 29Dec 4Dec 10Dec 16Dec 22Dec 28Jan 2Jan 7Jan 16
28°FDec 17Dec 25Jan 1Jan 4Jan 8Jan 13Jan 18Jan 28Feb 5
24°FJan 1Jan 5Jan 10Jan 14Jan 18Jan 22Jan 29Feb 2Feb 15
20°FJan 6Jan 11Jan 14Jan 18Jan 23Jan 27Jan 31Feb 4Feb 11
16°F–––––––––

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°F286278271265260256249243235
32°F318308302296290284278272262
28°F360344334327320312306299289
24°F365365365365351341334325312
20°F365365365365365365365354335
16°F365365365365365365365365365

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
92% of years
24°F or colder
62% of years
20°F or colder
25% of years
16°F or colder
8% 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
2,168
Cooling degree days, base 65°F
2,127
Growing degree days, base 40°F
9,141
Growing degree days, base 45°F
7,425
Growing degree days, base 50°F
5,830
Growing degree days, base 55°F
4,402
Growing degree days, base 60°F
3,169

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January528184
February447180
March3547168
April14345357
May26172611
June1375823
July0505970
August0487952
September1358807
October46144563
November21626275
December4066142

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 6.4 km from Hatteras. 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 USW00093729 (Cape Hatteras AP). Public domain.