Washington Boro climate

Washington Boro Frost Dates and Growing Season

NOAA 1991-2020 normals for Safe Harbor Dam, 10 km from Washington Boro, elevation 195 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Safe Harbor Dam. 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 1 and the first fall freeze around November 10, a growing season of about 221 days.

Median at 36°F
last April 13, first November 1
Median at 32°F
last April 1, first November 10
Median at 28°F
last March 22, first November 22

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 3Apr 27Apr 21Apr 16Apr 13Apr 10Apr 7Apr 5Apr 1
32°FApr 13Apr 9Apr 6Apr 3Apr 1Mar 31Mar 27Mar 24Mar 18
28°FApr 1Mar 30Mar 26Mar 24Mar 22Mar 19Mar 15Mar 11Mar 6
24°FMar 25Mar 21Mar 18Mar 15Mar 13Mar 9Mar 6Mar 2Feb 25
20°FMar 19Mar 14Mar 9Mar 7Mar 4Feb 28Feb 25Feb 17Feb 8
16°FMar 11Mar 5Feb 28Feb 25Feb 19Feb 13Feb 8Feb 2Jan 24

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 16Oct 21Oct 25Oct 29Nov 1Nov 2Nov 5Nov 8Nov 13
32°FOct 28Nov 2Nov 5Nov 8Nov 10Nov 13Nov 16Nov 20Nov 25
28°FNov 7Nov 12Nov 16Nov 19Nov 22Nov 25Nov 28Dec 1Dec 7
24°FNov 18Nov 24Nov 28Dec 1Dec 4Dec 8Dec 13Dec 19Dec 26
20°FDec 1Dec 6Dec 11Dec 17Dec 21Dec 25Dec 29Jan 3Jan 11
16°FDec 13Dec 21Dec 26Dec 31Jan 4Jan 9Jan 14Jan 20Jan 31

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°F216209205201198194188182174
32°F241234229224221217213208202
28°F264258253248244240236231225
24°F290283276271267262257252246
20°F316306302297292287281275266
16°F348333327320314308304299290

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
97% 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
4,908
Cooling degree days, base 65°F
1,164
Growing degree days, base 40°F
6,131
Growing degree days, base 45°F
4,842
Growing degree days, base 50°F
3,703
Growing degree days, base 55°F
2,715
Growing degree days, base 60°F
1,869

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,02101
February87103
March736023
April36112160
May13060397
June12237675
July0380845
August1320784
September40139549
October28016223
November585039
December87105

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 10 km from Washington Boro. 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 USC00367732 (Safe Harbor Dam). Public domain.