Brookhaven climate

Brookhaven Frost Dates and Growing Season

NOAA 1991-2020 normals for Morgantown Hart Fld, 3.6 km from Brookhaven, elevation 1240 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Morgantown Hart Fld. 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 23 and the first fall freeze around October 24, a growing season of about 182 days.

Median at 36°F
last May 4, first October 13
Median at 32°F
last April 23, first October 24
Median at 28°F
last April 10, first November 4

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 23May 16May 12May 8May 4May 1Apr 27Apr 24Apr 19
32°FMay 14May 6May 1Apr 27Apr 23Apr 20Apr 17Apr 13Apr 7
28°FApr 30Apr 22Apr 18Apr 14Apr 10Apr 7Apr 4Mar 31Mar 27
24°FApr 13Apr 7Apr 4Apr 1Mar 31Mar 27Mar 24Mar 19Mar 13
20°FApr 3Mar 30Mar 25Mar 21Mar 18Mar 14Mar 10Mar 5Feb 28
16°FMar 24Mar 18Mar 14Mar 10Mar 6Mar 3Feb 28Feb 21Feb 12

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°FSep 30Oct 4Oct 7Oct 10Oct 13Oct 15Oct 19Oct 21Oct 25
32°FOct 11Oct 15Oct 18Oct 21Oct 24Oct 27Oct 29Nov 1Nov 5
28°FOct 22Oct 27Oct 30Nov 1Nov 4Nov 6Nov 9Nov 13Nov 19
24°FNov 1Nov 5Nov 8Nov 12Nov 15Nov 19Nov 22Nov 28Dec 3
20°FNov 10Nov 16Nov 20Nov 24Nov 29Dec 3Dec 7Dec 13Dec 21
16°FNov 22Nov 30Dec 5Dec 10Dec 14Dec 19Dec 24Dec 28Jan 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°F179174169165161157152147139
32°F205197191187182178173168159
28°F230222217212208203198193184
24°F257248243237233228224219211
20°F285273266261257252247240230
16°F309300294288282277272265256

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
100% of years
16°F or colder
100% 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
4,964
Cooling degree days, base 65°F
930
Growing degree days, base 40°F
5,968
Growing degree days, base 45°F
4,662
Growing degree days, base 50°F
3,508
Growing degree days, base 55°F
2,498
Growing degree days, base 60°F
1,636

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,021011
February847013
March696255
April35417187
May14670395
June23182609
July1283747
August4245707
September66111496
October31818210
November603161
December885016

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 3.6 km from Brookhaven. 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 USW00013736 (Morgantown Hart Fld). Public domain.