Hebron climate

Hebron Frost Dates and Growing Season

NOAA 1991-2020 normals for Lake Geneva Wwtp, 14.3 km from Hebron, elevation 846 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lake Geneva Wwtp. 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 21, a growing season of about 179 days.

Median at 36°F
last May 5, first October 9
Median at 32°F
last April 25, first October 21
Median at 28°F
last April 12, first November 1

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

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°F176170165160156153149144138
32°F198192187182179175171165156
28°F222214210206203199195189182
24°F246238232228224219215211204
20°F266258253248243239234229221
16°F284277271267262257252247239

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
6,513
Cooling degree days, base 65°F
867
Growing degree days, base 40°F
5,196
Growing degree days, base 45°F
4,085
Growing degree days, base 50°F
3,091
Growing degree days, base 55°F
2,221
Growing degree days, base 60°F
1,473

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,31600
February1,09901
March907013
April511586
May20651321
June38175588
July3291753
August8236693
September9697454
October40011158
November777023
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 14.3 km from Hebron. 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 USC00474457 (Lake Geneva Wwtp). Public domain.