Collinsville climate

Collinsville Frost Dates and Growing Season

NOAA 1991-2020 normals for Burlington, 2.3 km from Collinsville, elevation 505 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Burlington. 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 25 and the first fall freeze around October 18, a growing season of about 172 days.

Median at 36°F
last May 6, first October 6
Median at 32°F
last April 25, first October 18
Median at 28°F
last April 13, first October 30

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

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 26Sep 30Oct 2Oct 4Oct 6Oct 9Oct 12Oct 16Oct 20
32°FOct 4Oct 9Oct 12Oct 15Oct 18Oct 20Oct 24Oct 27Nov 1
28°FOct 14Oct 19Oct 22Oct 26Oct 30Nov 2Nov 5Nov 9Nov 14
24°FOct 26Nov 1Nov 4Nov 8Nov 11Nov 14Nov 18Nov 24Dec 1
20°FNov 9Nov 14Nov 19Nov 23Nov 28Dec 1Dec 3Dec 6Dec 11
16°FNov 21Nov 27Dec 1Dec 3Dec 6Dec 9Dec 13Dec 18Dec 24

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°F170164160156152148145139131
32°F192185181176172168164159151
28°F217210205201197193189184175
24°F245238233228223219214208202
20°F270263257253248243238231223
16°F291284278273268263259253245

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
6,107
Cooling degree days, base 65°F
686
Growing degree days, base 40°F
4,986
Growing degree days, base 45°F
3,831
Growing degree days, base 50°F
2,830
Growing degree days, base 55°F
1,972
Growing degree days, base 60°F
1,254

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,18901
February1,01601
March892010
April520471
May22931279
June47124527
July5250710
August10199654
September10572419
October4076132
November686024
December1,00103

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 2.3 km from Collinsville. 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 USC00060973 (Burlington). Public domain.