Glenarden climate

Glenarden Frost Dates and Growing Season

NOAA 1991-2020 normals for Natl Arboretum Dc, 9.5 km from Glenarden, elevation 50 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Natl Arboretum Dc. 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 29 and the first fall freeze around November 8, a growing season of about 224 days.

Median at 36°F
last April 10, first October 29
Median at 32°F
last March 29, first November 8
Median at 28°F
last March 17, first November 20

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 28Apr 21Apr 16Apr 13Apr 10Apr 7Apr 4Apr 1Mar 29
32°FApr 11Apr 6Apr 3Mar 31Mar 29Mar 27Mar 24Mar 20Mar 15
28°FMar 31Mar 27Mar 24Mar 20Mar 17Mar 14Mar 11Mar 7Mar 2
24°FMar 22Mar 17Mar 14Mar 10Mar 7Mar 3Feb 28Feb 24Feb 17
20°FMar 13Mar 7Mar 3Feb 28Feb 23Feb 19Feb 14Feb 7Jan 31
16°FMar 2Feb 25Feb 18Feb 12Feb 6Feb 2Jan 29Jan 21Jan 13

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 20Oct 24Oct 26Oct 29Nov 1Nov 3Nov 6Nov 10
32°FOct 26Oct 31Nov 2Nov 5Nov 8Nov 10Nov 13Nov 17Nov 23
28°FNov 6Nov 11Nov 14Nov 17Nov 20Nov 25Nov 29Dec 2Dec 7
24°FNov 16Nov 23Nov 29Dec 2Dec 6Dec 10Dec 15Dec 21Dec 28
20°FDec 3Dec 10Dec 16Dec 22Dec 26Dec 30Jan 3Jan 9Jan 17
16°FDec 20Dec 27Jan 1Jan 5Jan 10Jan 14Jan 19Jan 25Feb 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°F219212208204200196191187179
32°F243236232227224220216212205
28°F272264257252248243239234229
24°F300292286279274269263257250
20°F330323316310304299293284275
16°F365349338333328323315308300

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
91% 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
4,049
Cooling degree days, base 65°F
1,649
Growing degree days, base 40°F
7,183
Growing degree days, base 45°F
5,768
Growing degree days, base 50°F
4,518
Growing degree days, base 55°F
3,417
Growing degree days, base 60°F
2,460

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January891011
February738014
March586370
April26929242
May75129520
June7329772
July0476941
August0422887
September21219648
October21038306
November492286
December759121

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 9.5 km from Glenarden. 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 USC00186350 (Natl Arboretum Dc). Public domain.