Green Level climate

Green Level Frost Dates and Growing Season

NOAA 1991-2020 normals for Apex, 7.5 km from Green Level, elevation 450 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Apex. 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 27 and the first fall freeze around November 8, a growing season of about 227 days.

Median at 36°F
last April 7, first October 31
Median at 32°F
last March 27, first November 8
Median at 28°F
last March 15, first November 21

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 9Apr 7Apr 4Apr 2Mar 29Mar 23
32°FApr 10Apr 6Apr 3Mar 31Mar 27Mar 24Mar 20Mar 16Mar 8
28°FMar 31Mar 26Mar 22Mar 18Mar 15Mar 10Mar 6Mar 2Feb 24
24°FMar 20Mar 14Mar 8Mar 5Mar 1Feb 26Feb 21Feb 13Feb 5
20°FMar 8Mar 1Feb 23Feb 16Feb 11Feb 6Jan 31Jan 24Jan 13
16°FFeb 25Feb 15Feb 6Feb 1Jan 30Jan 24Jan 18Jan 12Jan 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 17Oct 22Oct 25Oct 28Oct 31Nov 1Nov 4Nov 6Nov 11
32°FOct 26Nov 1Nov 3Nov 5Nov 8Nov 11Nov 14Nov 18Nov 24
28°FNov 5Nov 10Nov 13Nov 17Nov 21Nov 25Nov 30Dec 4Dec 12
24°FNov 18Nov 26Dec 1Dec 4Dec 9Dec 15Dec 23Jan 1Jan 9
20°FDec 5Dec 12Dec 21Dec 28Jan 1Jan 6Jan 12Jan 18Jan 28
16°FDec 16Dec 27Jan 1Jan 7Jan 13Jan 17Jan 23Jan 29Feb 6

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°F224217211208205201196192186
32°F251242237232227223219213206
28°F282273266259253249243238230
24°F315306298292286281274267257
20°F349335329322316309304297287
16°F365365361351343335331322310

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
96% of years
16°F or colder
73% 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
3,352
Cooling degree days, base 65°F
1,605
Growing degree days, base 40°F
7,642
Growing degree days, base 45°F
6,111
Growing degree days, base 50°F
4,739
Growing degree days, base 55°F
3,525
Growing degree days, base 60°F
2,483

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January747134
February603142
March4567128
April20442307
May59142549
June5319763
July0440905
August0389854
September17215648
October17844341
November4294118
December653250

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 7.5 km from Green Level. 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 USC00310212 (Apex). Public domain.