Westminster climate

Westminster Frost Dates and Growing Season

NOAA 1991-2020 normals for Lsu Ben-Hur Farm, 9.4 km from Westminster, elevation 21 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lsu Ben-Hur Farm. 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 February 28 and the first fall freeze around November 26, a growing season of about 272 days.

Median at 36°F
last March 16, first November 12
Median at 32°F
last February 28, first November 26
Median at 28°F
last February 7, first December 16

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 5Mar 31Mar 25Mar 20Mar 16Mar 12Mar 6Feb 28Feb 21
32°FMar 21Mar 16Mar 10Mar 4Feb 28Feb 24Feb 18Feb 9Jan 31
28°FMar 10Mar 1Feb 23Feb 15Feb 7Feb 1Jan 28Jan 20Jan 7
24°FFeb 26Feb 12Feb 2Jan 30Jan 24Jan 17Jan 12Jan 4Dec 24
20°FFeb 8Jan 31Jan 26Jan 21Jan 15Jan 10Jan 4Dec 31Dec 23
16°F–––––––––

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 29Nov 2Nov 5Nov 8Nov 12Nov 15Nov 19Nov 23Dec 1
32°FNov 6Nov 11Nov 15Nov 21Nov 26Nov 30Dec 4Dec 10Dec 22
28°FNov 20Nov 30Dec 4Dec 10Dec 16Dec 26Jan 1Jan 7Jan 16
24°FDec 5Dec 15Dec 24Dec 30Jan 2Jan 7Jan 12Jan 20Feb 2
20°FDec 16Dec 26Jan 1Jan 3Jan 7Jan 12Jan 18Jan 25Feb 1
16°F–––––––––

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°F272262255248242236231223212
32°F309295285279272265258250240
28°F347335327318309303293285273
24°F365365365357349341334327309
20°F365365365365365365365357340
16°F365365365365365365365365365

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
96% of years
24°F or colder
71% of years
20°F or colder
33% of years
16°F or colder
8% 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
1,693
Cooling degree days, base 65°F
2,571
Growing degree days, base 40°F
10,041
Growing degree days, base 45°F
8,297
Growing degree days, base 50°F
6,647
Growing degree days, base 55°F
5,130
Growing degree days, base 60°F
3,766

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January4587128
February31514173
March18244344
April64119507
May6299758
June0453903
July0521986
August0513978
September2387835
October51166581
November22234287
December39414168

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 9.4 km from Westminster. 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 USC00165620 (Lsu Ben-Hur Farm). Public domain.