Fort Hunt climate

Fort Hunt Frost Dates and Growing Season

NOAA 1991-2020 normals for Oxon Hill, 8.9 km from Fort Hunt, elevation 190 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Oxon Hill. 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 3 and the first fall freeze around November 8, a growing season of about 217 days.

Median at 36°F
last April 15, first October 27
Median at 32°F
last April 3, first November 8
Median at 28°F
last March 21, first November 19

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

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 14Oct 18Oct 21Oct 25Oct 27Oct 30Nov 1Nov 5Nov 10
32°FOct 24Oct 30Nov 1Nov 5Nov 8Nov 10Nov 13Nov 17Nov 23
28°FNov 5Nov 10Nov 14Nov 17Nov 19Nov 24Nov 29Dec 2Dec 8
24°FNov 17Nov 24Nov 29Dec 2Dec 5Dec 9Dec 14Dec 19Dec 25
20°FDec 2Dec 8Dec 13Dec 17Dec 23Dec 27Dec 31Jan 4Jan 13
16°FDec 14Dec 22Dec 28Jan 1Jan 4Jan 9Jan 14Jan 20Feb 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°F212207202198195190186181174
32°F240232226222217214210206200
28°F268260254249244240235230223
24°F294286281275270266260254248
20°F324314306300295290284279271
16°F355342333328323316309303295

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
93% 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
4,244
Cooling degree days, base 65°F
1,407
Growing degree days, base 40°F
6,807
Growing degree days, base 45°F
5,417
Growing degree days, base 50°F
4,190
Growing degree days, base 55°F
3,113
Growing degree days, base 60°F
2,184

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January913012
February759016
March609265
April29425220
May94100473
June7280723
July0415880
August0369834
September26185609
October23829272
November516171
December789016

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 8.9 km from Fort Hunt. 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 USC00186800 (Oxon Hill). Public domain.