Colfax climate

Colfax Frost Dates and Growing Season

NOAA 1991-2020 normals for Boyce 3 Wnw, 13.9 km from Colfax, elevation 110 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Boyce 3 Wnw. 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 2 and the first fall freeze around November 27, a growing season of about 271 days.

Median at 36°F
last March 15, first November 13
Median at 32°F
last March 2, first November 27
Median at 28°F
last February 11, first December 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°FApr 2Mar 28Mar 23Mar 19Mar 15Mar 11Mar 7Mar 2Feb 26
32°FMar 19Mar 14Mar 9Mar 5Mar 2Feb 26Feb 22Feb 14Feb 1
28°FMar 8Mar 2Feb 25Feb 18Feb 11Feb 4Jan 30Jan 25Jan 12
24°FFeb 28Feb 16Feb 7Feb 1Jan 29Jan 23Jan 16Jan 8Dec 29
20°FFeb 13Feb 3Jan 31Jan 28Jan 22Jan 16Jan 11Jan 5Dec 26
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 30Nov 3Nov 6Nov 10Nov 13Nov 17Nov 20Nov 26Dec 2
32°FNov 7Nov 13Nov 18Nov 23Nov 27Dec 1Dec 4Dec 9Dec 17
28°FNov 17Nov 27Dec 3Dec 8Dec 14Dec 22Dec 29Jan 4Jan 13
24°FDec 1Dec 15Dec 23Dec 29Jan 2Jan 7Jan 12Jan 18Feb 1
20°FDec 18Dec 30Jan 4Jan 7Jan 11Jan 15Jan 21Jan 31Feb 6
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°F269260254250244240233227219
32°F305292283277271265259252243
28°F341332324315307301291281270
24°F365365358350343335329319304
20°F365365365365365365359345332
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
98% of years
24°F or colder
78% of years
20°F or colder
36% of years
16°F or colder
9% 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
2,154
Cooling degree days, base 65°F
2,187
Growing degree days, base 40°F
9,236
Growing degree days, base 45°F
7,542
Growing degree days, base 50°F
5,967
Growing degree days, base 55°F
4,536
Growing degree days, base 60°F
3,267

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January546285
February3996117
March24424273
April8583451
May11242696
June0402852
July0485950
August0482947
September3325772
October80115503
November29216216
December4945105

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 13.9 km from Colfax. 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 USC00161232 (Boyce 3 Wnw). Public domain.