Alamance County climate

Alamance County Frost Dates and Growing Season

NOAA 1991-2020 normals for Haw Rvr 1E, 3.5 km from Alamance County, elevation 636 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Haw Rvr 1E. 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 4 and the first fall freeze around November 3, a growing season of about 215 days.

Median at 36°F
last April 15, first October 27
Median at 32°F
last April 4, first November 3
Median at 28°F
last March 20, first November 13

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 18Apr 15Apr 12Apr 9Apr 5Apr 1
32°FApr 19Apr 13Apr 10Apr 6Apr 4Mar 31Mar 27Mar 21Mar 15
28°FApr 8Apr 2Mar 29Mar 25Mar 20Mar 15Mar 11Mar 6Feb 28
24°FMar 26Mar 18Mar 12Mar 7Mar 2Feb 28Feb 24Feb 19Feb 8
20°FMar 11Mar 4Feb 28Feb 23Feb 17Feb 10Feb 4Jan 29Jan 18
16°FMar 1Feb 20Feb 11Feb 4Jan 31Jan 28Jan 21Jan 14Jan 3

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 15Oct 20Oct 22Oct 24Oct 27Oct 28Oct 31Nov 2Nov 6
32°FOct 24Oct 28Oct 30Nov 1Nov 3Nov 5Nov 8Nov 12Nov 17
28°FNov 1Nov 5Nov 8Nov 11Nov 13Nov 17Nov 20Nov 25Dec 3
24°FNov 10Nov 15Nov 19Nov 23Nov 27Dec 1Dec 5Dec 12Dec 24
20°FNov 22Nov 30Dec 5Dec 12Dec 21Dec 27Jan 1Jan 6Jan 15
16°FDec 10Dec 22Dec 29Jan 2Jan 6Jan 10Jan 16Jan 22Feb 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°F214207202198195191187182174
32°F237229224219215211207202195
28°F266258251246241236230225217
24°F302292284277270264259252243
20°F335327318311304298291284271
16°F365362349340334329322312302

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
83% 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
3,552
Cooling degree days, base 65°F
1,593
Growing degree days, base 40°F
7,483
Growing degree days, base 45°F
5,985
Growing degree days, base 50°F
4,653
Growing degree days, base 55°F
3,477
Growing degree days, base 60°F
2,461

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January797021
February629040
March4608129
April20938297
May58147554
June2320768
July0449914
August1379843
September17205637
October19344328
November485285
December701137

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 3.5 km from Alamance 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 USC00313919 (Haw Rvr 1E). Public domain.