Algonquin climate

Algonquin Frost Dates and Growing Season

NOAA 1991-2020 normals for Elgin, 11.5 km from Algonquin, elevation 763 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Elgin. 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 26 and the first fall freeze around October 18, a growing season of about 174 days.

Median at 36°F
last May 6, first October 7
Median at 32°F
last April 26, first October 18
Median at 28°F
last April 14, first October 29

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

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 24Sep 29Oct 1Oct 4Oct 7Oct 10Oct 12Oct 16Oct 21
32°FOct 3Oct 8Oct 12Oct 15Oct 18Oct 20Oct 23Oct 26Oct 31
28°FOct 15Oct 20Oct 24Oct 27Oct 29Nov 1Nov 3Nov 6Nov 12
24°FOct 27Oct 31Nov 3Nov 5Nov 8Nov 12Nov 15Nov 18Nov 23
20°FNov 5Nov 8Nov 13Nov 15Nov 19Nov 22Nov 25Nov 29Dec 3
16°FNov 11Nov 16Nov 20Nov 24Nov 27Nov 30Dec 3Dec 7Dec 15

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°F172165161157152148144139132
32°F193187182178174170165159152
28°F216210206201197194189184176
24°F240233228223219216211206200
20°F261255249244240236231225219
16°F280272268263259254250244235

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
6,592
Cooling degree days, base 65°F
807
Growing degree days, base 40°F
5,088
Growing degree days, base 45°F
3,978
Growing degree days, base 50°F
2,994
Growing degree days, base 55°F
2,134
Growing degree days, base 60°F
1,405

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,33000
February1,10601
March894120
April519486
May22448305
June40168578
July5273733
August10219674
September10986431
October4189143
November785021
December1,15302

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 11.5 km from Algonquin. 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 USC00112736 (Elgin). Public domain.