State Line climate

State Line Frost Dates and Growing Season

NOAA 1991-2020 normals for Hagerstown Washington CO AP, 2 km from State Line, elevation 698 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hagerstown Washington CO AP. 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 7 and the first fall freeze around November 4, a growing season of about 209 days.

Median at 36°F
last April 19, first October 23
Median at 32°F
last April 7, first November 4
Median at 28°F
last March 28, first November 14

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 7May 1Apr 26Apr 22Apr 19Apr 17Apr 14Apr 11Apr 6
32°FApr 21Apr 16Apr 12Apr 10Apr 7Apr 4Apr 2Mar 30Mar 25
28°FApr 8Apr 4Apr 2Mar 30Mar 28Mar 25Mar 22Mar 18Mar 13
24°FMar 31Mar 27Mar 23Mar 20Mar 17Mar 14Mar 11Mar 7Feb 28
20°FMar 22Mar 17Mar 13Mar 10Mar 7Mar 4Feb 28Feb 23Feb 14
16°FMar 14Mar 9Mar 5Mar 1Feb 27Feb 21Feb 13Feb 7Jan 30

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 9Oct 14Oct 17Oct 20Oct 23Oct 26Oct 28Nov 1Nov 5
32°FOct 22Oct 26Oct 29Nov 1Nov 4Nov 6Nov 8Nov 12Nov 17
28°FNov 1Nov 5Nov 9Nov 11Nov 14Nov 18Nov 22Nov 26Dec 2
24°FNov 11Nov 16Nov 20Nov 25Nov 29Dec 2Dec 6Dec 11Dec 17
20°FNov 24Dec 1Dec 5Dec 9Dec 14Dec 19Dec 22Dec 27Jan 2
16°FDec 8Dec 14Dec 21Dec 25Dec 28Jan 1Jan 6Jan 12Jan 20

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°F206199194189186181176171165
32°F228222218213209205201196189
28°F256247242236232227224219212
24°F282274267262257253248242234
20°F306298293288282277271266256
16°F331322315309304300295289281

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
4,716
Cooling degree days, base 65°F
1,248
Growing degree days, base 40°F
6,381
Growing degree days, base 45°F
5,062
Growing degree days, base 50°F
3,893
Growing degree days, base 55°F
2,868
Growing degree days, base 60°F
1,984

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January99506
February828010
March671150
April33220193
May11093450
June10255695
July0391856
August2321784
September45145551
October27922236
November573051
December871011

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 2 km from State Line. 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 USW00093706 (Hagerstown Washington CO AP). Public domain.