Washington County climate

Washington County Frost Dates and Growing Season

NOAA 1991-2020 normals for Stoneville Exp Stn, 16.7 km from Washington County, elevation 127 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Stoneville Exp Stn. 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 11 and the first fall freeze around November 16, a growing season of about 250 days.

Median at 36°F
last March 24, first November 5
Median at 32°F
last March 11, first November 16
Median at 28°F
last February 27, first December 1

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 10Apr 4Mar 31Mar 28Mar 24Mar 21Mar 17Mar 12Mar 4
32°FMar 28Mar 23Mar 18Mar 14Mar 11Mar 7Mar 3Feb 28Feb 20
28°FMar 16Mar 10Mar 6Mar 2Feb 27Feb 22Feb 17Feb 10Feb 1
24°FMar 6Feb 28Feb 18Feb 12Feb 6Jan 31Jan 28Jan 21Jan 9
20°FFeb 25Feb 12Feb 3Jan 31Jan 27Jan 21Jan 15Jan 9Dec 31
16°FFeb 12Feb 3Jan 31Jan 25Jan 20Jan 15Jan 10Jan 4Dec 29

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 22Oct 26Oct 30Nov 1Nov 5Nov 8Nov 11Nov 15Nov 21
32°FNov 1Nov 5Nov 9Nov 12Nov 16Nov 20Nov 25Nov 30Dec 4
28°FNov 9Nov 15Nov 22Nov 28Dec 1Dec 6Dec 12Dec 22Jan 1
24°FNov 27Dec 4Dec 13Dec 22Dec 27Jan 1Jan 4Jan 11Jan 21
20°FDec 11Dec 25Dec 30Jan 2Jan 7Jan 12Jan 18Jan 26Feb 2
16°FDec 23Jan 1Jan 3Jan 7Jan 12Jan 17Jan 21Jan 28Feb 4

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°F249241235230225221217211204
32°F277268262255250245240233226
28°F315301293287280272266259249
24°F352339332324317308300292279
20°F365365363354345337333325311
16°F365365365365365365354343332

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
96% of years
20°F or colder
74% of years
16°F or colder
37% 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
2,639
Cooling degree days, base 65°F
2,398
Growing degree days, base 40°F
9,050
Growing degree days, base 45°F
7,434
Growing degree days, base 50°F
5,955
Growing degree days, base 55°F
4,622
Growing degree days, base 60°F
3,435

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January669251
February494379
March31922224
April10896444
May12277730
June0453903
July05391,004
August0518983
September6348792
October103118486
November34218187
December586575

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 16.7 km from Washington County. 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 USC00228445 (Stoneville Exp Stn). Public domain.