Wake County climate

Wake County Frost Dates and Growing Season

NOAA 1991-2020 normals for Raleigh State Univ, 4.4 km from Wake County, elevation 400 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Raleigh State Univ. 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 28 and the first fall freeze around November 8, a growing season of about 229 days.

Median at 36°F
last April 7, first October 31
Median at 32°F
last March 28, first November 8
Median at 28°F
last March 14, first November 23

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 21Apr 16Apr 13Apr 10Apr 7Apr 5Apr 2Mar 30Mar 25
32°FApr 12Apr 7Apr 3Apr 1Mar 28Mar 24Mar 20Mar 16Mar 8
28°FMar 31Mar 25Mar 20Mar 17Mar 14Mar 9Mar 5Feb 28Feb 22
24°FMar 19Mar 11Mar 7Mar 3Feb 28Feb 24Feb 18Feb 11Feb 2
20°FMar 7Feb 28Feb 23Feb 15Feb 9Feb 3Jan 31Jan 23Jan 13
16°FFeb 25Feb 14Feb 5Jan 31Jan 28Jan 23Jan 17Jan 12Jan 5

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 18Oct 23Oct 26Oct 29Oct 31Nov 2Nov 5Nov 8Nov 14
32°FOct 28Nov 1Nov 4Nov 6Nov 8Nov 12Nov 16Nov 20Nov 27
28°FNov 6Nov 11Nov 15Nov 19Nov 23Nov 27Dec 1Dec 6Dec 15
24°FNov 18Nov 26Dec 1Dec 5Dec 10Dec 17Dec 23Dec 31Jan 7
20°FDec 4Dec 12Dec 19Dec 26Jan 1Jan 5Jan 10Jan 16Jan 26
16°FDec 23Jan 1Jan 4Jan 8Jan 12Jan 16Jan 22Jan 27Feb 5

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°F227220215210207203199195187
32°F255245240234229224219215208
28°F284275266260254249244238230
24°F321307300294287280273266256
20°F358343333325317310305300289
16°F365365365357347339333322309

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
69% 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
3,165
Cooling degree days, base 65°F
1,779
Growing degree days, base 40°F
7,948
Growing degree days, base 45°F
6,389
Growing degree days, base 50°F
4,990
Growing degree days, base 55°F
3,757
Growing degree days, base 60°F
2,687

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January724034
February583139
March4318138
April18047329
May41166591
June3353799
July0479944
August0426891
September12242679
October15451370
November4094126
December628250

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 4.4 km from Wake County. 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 USC00317079 (Raleigh State Univ). Public domain.