South Beloit climate

South Beloit Frost Dates and Growing Season

NOAA 1991-2020 normals for Beloit, 1.3 km from South Beloit, elevation 788 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Beloit. 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 May 1 and the first fall freeze around October 12, a growing season of about 162 days.

Median at 36°F
last May 11, first October 1
Median at 32°F
last May 1, first October 12
Median at 28°F
last April 20, first October 23

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 27May 22May 18May 15May 11May 8May 5May 2Apr 29
32°FMay 16May 11May 7May 4May 1Apr 29Apr 26Apr 22Apr 17
28°FMay 4Apr 30Apr 26Apr 22Apr 20Apr 17Apr 13Apr 9Apr 4
24°FApr 22Apr 18Apr 14Apr 10Apr 7Apr 4Apr 2Mar 31Mar 24
20°FApr 10Apr 6Apr 3Apr 1Mar 31Mar 27Mar 22Mar 18Mar 13
16°FApr 2Mar 30Mar 26Mar 22Mar 19Mar 16Mar 13Mar 9Mar 4

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 21Sep 24Sep 27Sep 30Oct 1Oct 4Oct 7Oct 9Oct 14
32°FSep 28Oct 2Oct 6Oct 9Oct 12Oct 15Oct 18Oct 21Oct 24
28°FOct 9Oct 14Oct 17Oct 21Oct 23Oct 25Oct 28Oct 31Nov 4
24°FOct 20Oct 25Oct 29Oct 31Nov 2Nov 5Nov 9Nov 12Nov 17
20°FNov 1Nov 5Nov 8Nov 11Nov 14Nov 17Nov 19Nov 23Nov 27
16°FNov 8Nov 13Nov 17Nov 20Nov 22Nov 25Nov 28Dec 1Dec 6

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°F161155150146143139135130124
32°F182176171166162158154150144
28°F204199194189186181177173165
24°F227220215212207204201197188
20°F250242237233228225220216210
16°F268261256252248244239235227

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
7,570
Cooling degree days, base 65°F
467
Growing degree days, base 40°F
4,308
Growing degree days, base 45°F
3,283
Growing degree days, base 50°F
2,380
Growing degree days, base 55°F
1,607
Growing degree days, base 60°F
960

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,46000
February1,21400
March1,003011
April614252
May30226228
June71100479
July19165611
August31125559
September17246334
October515495
November891010
December1,27901

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 1.3 km from South Beloit. 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 USC00470696 (Beloit). Public domain.