Pontiac climate

Pontiac Frost Dates and Growing Season

NOAA 1991-2020 normals for Pontiac, 0.6 km from Pontiac, elevation 650 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Pontiac. 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 16 and the first fall freeze around October 24, a growing season of about 191 days.

Median at 36°F
last April 26, first October 15
Median at 32°F
last April 16, first October 24
Median at 28°F
last April 4, first November 3

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 11May 6May 3Apr 30Apr 26Apr 23Apr 20Apr 17Apr 13
32°FMay 2Apr 26Apr 22Apr 19Apr 16Apr 13Apr 10Apr 7Apr 3
28°FApr 19Apr 14Apr 10Apr 7Apr 4Apr 2Apr 1Mar 28Mar 20
24°FApr 9Apr 4Apr 1Mar 30Mar 26Mar 23Mar 19Mar 15Mar 9
20°FMar 31Mar 27Mar 22Mar 18Mar 15Mar 11Mar 9Mar 4Feb 27
16°FMar 23Mar 17Mar 14Mar 11Mar 7Mar 4Mar 1Feb 24Feb 17

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 2Oct 6Oct 10Oct 12Oct 15Oct 17Oct 20Oct 23Oct 27
32°FOct 12Oct 17Oct 20Oct 22Oct 24Oct 27Oct 30Nov 1Nov 5
28°FOct 23Oct 27Oct 30Nov 1Nov 3Nov 6Nov 9Nov 13Nov 18
24°FNov 1Nov 5Nov 8Nov 11Nov 14Nov 17Nov 21Nov 24Nov 29
20°FNov 8Nov 13Nov 17Nov 21Nov 24Nov 27Dec 1Dec 5Dec 11
16°FNov 14Nov 21Nov 25Nov 29Dec 2Dec 5Dec 9Dec 15Dec 20

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°F188182178174170166162157150
32°F210203198194191187182178171
28°F234227221217213209205199192
24°F256249242238234230226221214
20°F277270263259255250245240232
16°F294285279274270266261256249

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
5,840
Cooling degree days, base 65°F
1,052
Growing degree days, base 40°F
5,763
Growing degree days, base 45°F
4,570
Growing degree days, base 50°F
3,503
Growing degree days, base 55°F
2,555
Growing degree days, base 60°F
1,737

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,24601
February1,01503
March788239
April41112146
May15285405
June20231661
July2312775
August5263722
September72129509
October34319200
November710137
December1,07704

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 0.6 km from Pontiac. 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 USC00116910 (Pontiac). Public domain.