Delavan climate

Delavan Frost Dates and Growing Season

NOAA 1991-2020 normals for Delavan Wwtp, 1.4 km from Delavan, elevation 882 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Delavan 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 28 and the first fall freeze around October 14, a growing season of about 168 days.

Median at 36°F
last May 10, first October 3
Median at 32°F
last April 28, first October 14
Median at 28°F
last April 15, first October 25

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 26May 21May 17May 13May 10May 7May 3Apr 30Apr 26
32°FMay 14May 8May 4Apr 30Apr 28Apr 24Apr 20Apr 17Apr 12
28°FMay 1Apr 26Apr 22Apr 18Apr 15Apr 12Apr 9Apr 6Apr 2
24°FApr 18Apr 13Apr 8Apr 5Apr 3Mar 31Mar 29Mar 24Mar 17
20°FApr 6Apr 2Mar 31Mar 27Mar 24Mar 20Mar 17Mar 13Mar 8
16°FMar 29Mar 24Mar 20Mar 17Mar 13Mar 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 20Sep 24Sep 28Oct 1Oct 3Oct 6Oct 8Oct 12Oct 15
32°FSep 28Oct 3Oct 7Oct 11Oct 14Oct 16Oct 19Oct 22Oct 26
28°FOct 8Oct 15Oct 19Oct 23Oct 25Oct 28Oct 31Nov 3Nov 8
24°FOct 25Oct 30Nov 1Nov 4Nov 7Nov 10Nov 14Nov 17Nov 22
20°FNov 4Nov 9Nov 12Nov 15Nov 18Nov 21Nov 25Nov 29Dec 3
16°FNov 13Nov 17Nov 22Nov 26Nov 29Dec 2Dec 5Dec 9Dec 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°F165158153149145140136131124
32°F188181176172168164158152146
28°F213205200196192188184178170
24°F240233228223218213209204197
20°F262254249245240237233227220
16°F282274268264259255250245237

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
6,933
Cooling degree days, base 65°F
631
Growing degree days, base 40°F
4,706
Growing degree days, base 45°F
3,636
Growing degree days, base 50°F
2,696
Growing degree days, base 55°F
1,880
Growing degree days, base 60°F
1,180

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,35400
February1,14000
March953221
April561156
May25432273
June41128537
July9221677
August19174620
September13869386
October4644113
November824013
December1,17601

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 1.4 km from Delavan. 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 USC00472051 (Delavan Wwtp). Public domain.