Chappell climate

Chappell Frost Dates and Growing Season

NOAA 1991-2020 normals for Chappell, 0.1 km from Chappell, elevation 3710 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Chappell. 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 May 8 and the first fall freeze around October 5, a growing season of about 149 days.

Median at 36°F
last May 19, first September 26
Median at 32°F
last May 8, first October 5
Median at 28°F
last April 28, first October 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°FJun 3May 29May 24May 21May 19May 16May 13May 10May 6
32°FMay 21May 16May 13May 10May 8May 6May 3Apr 30Apr 24
28°FMay 11May 7May 4May 1Apr 28Apr 25Apr 21Apr 17Apr 12
24°FMay 2Apr 27Apr 23Apr 19Apr 16Apr 12Apr 9Apr 5Mar 31
20°FApr 22Apr 16Apr 12Apr 9Apr 5Apr 2Mar 30Mar 25Mar 20
16°FApr 12Apr 6Apr 3Mar 31Mar 26Mar 21Mar 17Mar 12Mar 6

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°FSep 11Sep 17Sep 20Sep 24Sep 26Sep 29Oct 1Oct 4Oct 8
32°FSep 20Sep 26Sep 30Oct 3Oct 5Oct 7Oct 10Oct 13Oct 16
28°FOct 1Oct 5Oct 9Oct 11Oct 14Oct 16Oct 18Oct 21Oct 24
24°FOct 10Oct 14Oct 17Oct 19Oct 22Oct 24Oct 27Oct 30Nov 2
20°FOct 16Oct 21Oct 24Oct 27Oct 30Nov 1Nov 4Nov 8Nov 13
16°FOct 22Oct 29Nov 1Nov 4Nov 8Nov 11Nov 14Nov 18Nov 22

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°F147141137133130126121116109
32°F165160156153149145142137131
28°F187180175172168165160156149
24°F208201196192187183178174168
20°F228221215211206202198193185
16°F249242235231226220216210201

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
100% of years
20°F or colder
100% of years
16°F or colder
100% 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
6,660
Cooling degree days, base 65°F
708
Growing degree days, base 40°F
4,804
Growing degree days, base 45°F
3,700
Growing degree days, base 50°F
2,743
Growing degree days, base 55°F
1,932
Growing degree days, base 60°F
1,255

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,19500
February1,02002
March837016
April555166
May28226252
June56125520
July6278737
August17217665
September14059378
October511298
November86109
December1,18101

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 0.1 km from Chappell. 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 USC00251602 (Chappell). Public domain.