Wittmann climate

Wittmann Frost Dates and Growing Season

NOAA 1991-2020 normals for Wittmann 1SE, 0.5 km from Wittmann, elevation 1683 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Wittmann 1SE. 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 5 and the first fall freeze around December 11, a growing season of about 306 days.

Median at 36°F
last March 4, first November 26
Median at 32°F
last February 5, first December 11
Median at 28°F
last January 15, first December 27

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 2Mar 21Mar 14Mar 9Mar 4Feb 28Feb 21Feb 15Feb 6
32°FMar 3Feb 24Feb 16Feb 11Feb 5Jan 31Jan 24Jan 16Jan 6
28°FFeb 12Feb 5Jan 30Jan 22Jan 15Jan 9Jan 3Dec 27Dec 14
24°FFeb 5Jan 30Jan 22Jan 19Jan 11Jan 6Jan 1Dec 28Dec 22
20°F–––––––––
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°FNov 8Nov 16Nov 20Nov 24Nov 26Dec 1Dec 5Dec 9Dec 14
32°FNov 20Nov 26Dec 2Dec 7Dec 11Dec 15Dec 19Dec 25Jan 2
28°FDec 4Dec 12Dec 17Dec 23Dec 27Dec 30Jan 5Jan 14Jan 28
24°FDec 19Dec 27Dec 30Jan 1Jan 7Jan 15Jan 21Jan 27Feb 3
20°F–––––––––
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°F297284277271266258251243232
32°F341330321313306300291282270
28°F365365359352345339332322311
24°F365365365365365365365365347
20°F365365365365365365365365365
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
99% of years
28°F or colder
76% of years
24°F or colder
23% of years
20°F or colder
2% of years
16°F or colder
0% 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
1,533
Cooling degree days, base 65°F
3,471
Growing degree days, base 40°F
11,068
Growing degree days, base 45°F
9,269
Growing degree days, base 50°F
7,546
Growing degree days, base 55°F
5,977
Growing degree days, base 60°F
4,619

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January3970113
February2871158
March17124323
April59100491
May6343801
June06131,063
July07971,262
August07781,243
September05611,011
October18229676
November17826306
December4170100

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 0.5 km from Wittmann. 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 USC00029464 (Wittmann 1SE). Public domain.