Williston climate

Williston Frost Dates and Growing Season

NOAA 1991-2020 normals for Blackville 3 W, 10.1 km from Williston, elevation 317 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Blackville 3 W. 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 20 and the first fall freeze around November 13, a growing season of about 238 days.

Median at 36°F
last April 2, first November 2
Median at 32°F
last March 20, first November 13
Median at 28°F
last March 5, first November 30

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 18Apr 12Apr 8Apr 5Apr 2Mar 30Mar 27Mar 22Mar 16
32°FApr 8Apr 2Mar 28Mar 24Mar 20Mar 16Mar 12Mar 6Feb 27
28°FMar 26Mar 19Mar 15Mar 10Mar 5Mar 1Feb 24Feb 17Feb 6
24°FMar 14Mar 5Feb 28Feb 19Feb 12Feb 6Feb 2Jan 27Jan 17
20°FFeb 28Feb 17Feb 6Feb 1Jan 29Jan 22Jan 16Jan 9Dec 30
16°FFeb 12Feb 3Jan 30Jan 25Jan 20Jan 15Jan 9Jan 2Dec 27

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 20Oct 25Oct 28Oct 31Nov 2Nov 5Nov 8Nov 11Nov 17
32°FOct 29Nov 3Nov 6Nov 9Nov 13Nov 16Nov 22Nov 26Dec 2
28°FNov 9Nov 16Nov 20Nov 25Nov 30Dec 3Dec 7Dec 13Dec 28
24°FNov 24Dec 1Dec 6Dec 12Dec 20Dec 29Jan 2Jan 8Jan 16
20°FDec 5Dec 13Dec 24Jan 1Jan 4Jan 9Jan 14Jan 21Feb 1
16°FDec 14Dec 26Jan 1Jan 7Jan 12Jan 16Jan 21Jan 30Feb 5

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°F238230224219213209204200193
32°F266256249243238233228222212
28°F302291282275269262256249240
24°F342331321311305298291283270
20°F365365352344336331321309299
16°F365365365365365365353339327

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
77% of years
16°F or colder
39% 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
2,383
Cooling degree days, base 65°F
2,006
Growing degree days, base 40°F
8,836
Growing degree days, base 45°F
7,163
Growing degree days, base 50°F
5,629
Growing degree days, base 55°F
4,252
Growing degree days, base 60°F
3,034

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January586275
February439595
March29415226
April11363404
May16219668
June0386835
July0485950
August0445910
September5287732
October9685457
November32013184
December515394

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 10.1 km from Williston. 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 USW00063826 (Blackville 3 W). Public domain.