Sultan climate

Sultan Frost Dates and Growing Season

NOAA 1991-2020 normals for Startup 1 E, 7.4 km from Sultan, elevation 170 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Startup 1 E. 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 15 and the first fall freeze around October 25, a growing season of about 192 days.

Median at 36°F
last May 8, first October 7
Median at 32°F
last April 15, first October 25
Median at 28°F
last March 18, first November 12

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 24May 20May 15May 11May 8May 4May 1Apr 26Apr 20
32°FMay 7May 1Apr 26Apr 20Apr 15Apr 10Apr 6Apr 1Mar 25
28°FApr 11Apr 3Mar 27Mar 22Mar 18Mar 13Mar 8Mar 2Feb 22
24°FMar 16Mar 7Mar 1Feb 25Feb 19Feb 13Feb 5Jan 22Jan 2
20°FFeb 26Feb 16Feb 3Jan 22Jan 12Jan 2Dec 23Dec 14Dec 5
16°FJan 31Jan 13Jan 4Dec 31Dec 21Dec 16Dec 10Dec 5Nov 30

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 22Sep 28Oct 1Oct 5Oct 7Oct 11Oct 15Oct 20Oct 25
32°FOct 5Oct 13Oct 17Oct 21Oct 25Oct 28Nov 1Nov 7Nov 15
28°FOct 23Oct 29Nov 2Nov 7Nov 12Nov 19Nov 26Dec 1Dec 12
24°FNov 7Nov 15Nov 22Nov 29Dec 3Dec 9Dec 18Dec 29Jan 14
20°FNov 18Nov 27Dec 2Dec 7Dec 14Dec 20Dec 30Jan 8Jan 29
16°FNov 23Dec 1Dec 5Dec 8Dec 13Dec 20Dec 28Jan 2Jan 18

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°F179170164159154149143137127
32°F222212204198192186179172162
28°F280265255248240232225216205
24°F340324313304294284275264252
20°F365365361350340334326317302
16°F365365365365365365360344333

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
98% of years
20°F or colder
73% of years
16°F or colder
38% 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
5,024
Cooling degree days, base 65°F
147
Growing degree days, base 40°F
4,466
Growing degree days, base 45°F
3,031
Growing degree days, base 50°F
1,904
Growing degree days, base 55°F
1,062
Growing degree days, base 60°F
477

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January75305
February63407
March608020
April463161
May3017187
June17417293
July6755453
August5855462
September16613298
October414099
November612018
December77303

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 7.4 km from Sultan. 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 USC00458034 (Startup 1 E). Public domain.