Williams climate

Williams Frost Dates and Growing Season

NOAA 1991-2020 normals for Williams, 1 km from Williams, elevation 6909 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Williams. 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 22 and the first fall freeze around October 5, a growing season of about 135 days.

Median at 36°F
last June 2, first September 30
Median at 32°F
last May 22, first October 5
Median at 28°F
last May 9, first October 15

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 17Jun 11Jun 7Jun 5Jun 2May 31May 28May 24May 19
32°FJun 10Jun 4May 31May 27May 22May 18May 15May 11May 6
28°FJun 1May 23May 17May 13May 9May 6May 2Apr 30Apr 24
24°FMay 12May 6May 2Apr 29Apr 25Apr 21Apr 17Apr 12Apr 7
20°FApr 26Apr 20Apr 14Apr 9Apr 6Apr 2Mar 30Mar 24Mar 15
16°FApr 10Apr 3Mar 28Mar 23Mar 17Mar 13Mar 8Mar 3Feb 24

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 17Sep 21Sep 24Sep 27Sep 30Oct 1Oct 3Oct 6Oct 10
32°FSep 24Sep 29Oct 1Oct 3Oct 5Oct 8Oct 10Oct 14Oct 18
28°FOct 2Oct 5Oct 9Oct 12Oct 15Oct 18Oct 21Oct 25Oct 31
24°FOct 10Oct 15Oct 19Oct 24Oct 27Oct 31Nov 3Nov 8Nov 14
20°FOct 21Oct 27Nov 1Nov 4Nov 8Nov 12Nov 16Nov 20Nov 25
16°FOct 31Nov 7Nov 13Nov 16Nov 20Nov 24Nov 28Dec 3Dec 8

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°F13612912412111711410910498
32°F157150145139135130126120112
28°F181173168163159154149143134
24°F210201195190185181175169161
20°F242232225220215210202196187
16°F276266258252246239233224213

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
5,671
Cooling degree days, base 65°F
298
Growing degree days, base 40°F
4,480
Growing degree days, base 45°F
3,271
Growing degree days, base 50°F
2,269
Growing degree days, base 55°F
1,442
Growing degree days, base 60°F
781

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January95200
February81300
March73807
April546043
May3126196
June6964447
July9128584
August2280524
September12318348
October4230108
November701012
December96400

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 km from Williams. 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 USC00029359 (Williams). Public domain.