Willow climate

Willow Frost Dates and Growing Season

NOAA 1991-2020 normals for Willow West, 0.9 km from Willow, elevation 205 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Willow West. 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 15 and the first fall freeze around September 18, a growing season of about 126 days.

Median at 36°F
last May 28, first September 7
Median at 32°F
last May 15, first September 18
Median at 28°F
last May 3, first September 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°FJun 9Jun 4Jun 1May 30May 28May 25May 22May 19May 15
32°FMay 28May 24May 21May 17May 15May 12May 9May 6May 3
28°FMay 17May 12May 8May 5May 3May 2Apr 30Apr 27Apr 21
24°FMay 6May 2Apr 30Apr 27Apr 24Apr 21Apr 18Apr 15Apr 12
20°FApr 28Apr 23Apr 20Apr 17Apr 15Apr 12Apr 10Apr 7Apr 4
16°FApr 21Apr 16Apr 13Apr 10Apr 8Apr 6Apr 4Apr 3Mar 31

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°FAug 25Aug 29Sep 1Sep 4Sep 7Sep 10Sep 13Sep 16Sep 20
32°FSep 4Sep 9Sep 13Sep 16Sep 18Sep 20Sep 22Sep 25Sep 28
28°FSep 14Sep 19Sep 22Sep 25Sep 27Sep 29Oct 1Oct 4Oct 9
24°FSep 23Sep 27Sep 30Oct 3Oct 5Oct 8Oct 11Oct 14Oct 19
20°FSep 30Oct 4Oct 8Oct 11Oct 13Oct 16Oct 19Oct 23Oct 28
16°FOct 6Oct 11Oct 14Oct 17Oct 20Oct 22Oct 25Oct 29Nov 3

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°F11911310810410097938983
32°F145139134130126122118113107
28°F165159154150146143138134127
24°F184177173168165161157152146
20°F199192188184181178174168162
16°F212205201197194190187182175

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
11,521
Cooling degree days, base 65°F
19
Growing degree days, base 40°F
2,178
Growing degree days, base 45°F
1,425
Growing degree days, base 50°F
808
Growing degree days, base 55°F
354
Growing degree days, base 60°F
102

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,83800
February1,44600
March1,36900
April88501
May540038
June2546209
July16210313
August2573214
September528032
October1,01401
November1,48600
December1,74200

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 0.9 km from Willow. 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 USC00509861 (Willow West). Public domain.