King William climate

King William Frost Dates and Growing Season

NOAA 1991-2020 normals for Walkerton 2 Nw, 6.7 km from King William, elevation 50 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Walkerton 2 Nw. 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 7 and the first fall freeze around November 1, a growing season of about 209 days.

Median at 36°F
last April 19, first October 23
Median at 32°F
last April 7, first November 1
Median at 28°F
last March 27, first November 11

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 4Apr 29Apr 25Apr 22Apr 19Apr 16Apr 13Apr 10Apr 4
32°FApr 23Apr 18Apr 14Apr 10Apr 7Apr 3Mar 31Mar 29Mar 24
28°FApr 11Apr 5Apr 1Mar 30Mar 27Mar 24Mar 20Mar 16Mar 8
24°FApr 1Mar 27Mar 23Mar 18Mar 14Mar 9Mar 5Feb 28Feb 22
20°FMar 24Mar 14Mar 8Mar 4Feb 28Feb 24Feb 20Feb 12Feb 3
16°FMar 9Feb 28Feb 24Feb 18Feb 11Feb 6Feb 1Jan 25Jan 15

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 10Oct 14Oct 17Oct 20Oct 23Oct 25Oct 27Oct 30Nov 3
32°FOct 18Oct 24Oct 26Oct 30Nov 1Nov 3Nov 5Nov 9Nov 14
28°FOct 29Nov 2Nov 5Nov 9Nov 11Nov 14Nov 17Nov 23Dec 1
24°FNov 8Nov 13Nov 17Nov 21Nov 24Nov 29Dec 2Dec 6Dec 15
20°FNov 21Nov 28Dec 2Dec 6Dec 11Dec 16Dec 22Dec 29Jan 5
16°FDec 6Dec 13Dec 20Dec 25Dec 30Jan 3Jan 8Jan 14Jan 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°F206199194190186183179174167
32°F228221217212209205201197189
28°F255247240235231227222217210
24°F283274267261255251245239231
20°F315304298292285279273267256
16°F346334328320314307301294282

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
97% 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
3,610
Cooling degree days, base 65°F
1,563
Growing degree days, base 40°F
7,428
Growing degree days, base 45°F
5,941
Growing degree days, base 50°F
4,611
Growing degree days, base 55°F
3,438
Growing degree days, base 60°F
2,421

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January806025
February653029
March4997109
April21543296
May64132533
June5304748
July0431896
August0383848
September21213642
October18446338
November4514112
December712135

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 6.7 km from King William. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00448829 (Walkerton 2 Nw). Public domain.