Chelan climate

Chelan Frost Dates and Growing Season

NOAA 1991-2020 normals for Chelan, 1.4 km from Chelan, elevation 1194 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Chelan. 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 April 17 and the first fall freeze around October 22, a growing season of about 187 days.

Median at 36°F
last May 1, first October 10
Median at 32°F
last April 17, first October 22
Median at 28°F
last March 29, first November 4

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°FMay 15May 9May 5May 3May 1Apr 29Apr 26Apr 24Apr 19
32°FApr 30Apr 27Apr 24Apr 21Apr 17Apr 14Apr 12Apr 8Apr 3
28°FApr 15Apr 8Apr 3Mar 31Mar 29Mar 25Mar 21Mar 16Mar 11
24°FMar 28Mar 20Mar 16Mar 13Mar 10Mar 7Mar 4Mar 2Feb 24
20°FMar 14Mar 8Mar 4Mar 2Feb 28Feb 24Feb 20Feb 15Feb 7
16°FMar 4Feb 28Feb 23Feb 19Feb 14Feb 9Feb 3Jan 26Jan 13

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 1Oct 3Oct 5Oct 8Oct 10Oct 12Oct 16Oct 18Oct 22
32°FOct 9Oct 13Oct 17Oct 20Oct 22Oct 25Oct 28Oct 31Nov 5
28°FOct 21Oct 25Oct 29Nov 1Nov 4Nov 6Nov 9Nov 13Nov 18
24°FOct 30Nov 6Nov 9Nov 12Nov 15Nov 18Nov 21Nov 24Nov 30
20°FNov 10Nov 15Nov 20Nov 24Nov 27Dec 1Dec 5Dec 11Dec 20
16°FNov 20Nov 27Dec 1Dec 5Dec 10Dec 16Dec 22Dec 31Jan 9

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°F177172168164161157154149143
32°F206200195191187184180176170
28°F242235229223219215210204196
24°F271263257253248243240232223
20°F304294287280274269264258248
16°F338326317310303297291283274

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
99% 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
6,037
Cooling degree days, base 65°F
652
Growing degree days, base 40°F
4,854
Growing degree days, base 45°F
3,700
Growing degree days, base 50°F
2,710
Growing degree days, base 55°F
1,872
Growing degree days, base 60°F
1,181

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,14900
February89600
March74103
April456063
May20722287
June6781464
July9253708
August9243699
September10753397
October450188
November82201
December1,12400

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 1.4 km from Chelan. 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 USC00451350 (Chelan). Public domain.