Iola climate

Iola Frost Dates and Growing Season

NOAA 1991-2020 normals for Waupaca, 18 km from Iola, elevation 837 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Waupaca. 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 8 and the first fall freeze around October 6, a growing season of about 151 days.

Median at 36°F
last May 19, first September 27
Median at 32°F
last May 8, first October 6
Median at 28°F
last April 28, first October 17

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 31May 27May 24May 22May 19May 16May 13May 9May 4
32°FMay 21May 16May 13May 10May 8May 4May 1Apr 29Apr 24
28°FMay 11May 6May 2Apr 30Apr 28Apr 25Apr 21Apr 18Apr 12
24°FApr 30Apr 26Apr 22Apr 18Apr 16Apr 12Apr 9Apr 6Apr 2
20°FApr 19Apr 14Apr 10Apr 7Apr 5Apr 2Apr 1Mar 29Mar 22
16°FApr 10Apr 5Apr 2Mar 31Mar 28Mar 25Mar 22Mar 18Mar 12

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 14Sep 19Sep 22Sep 25Sep 27Sep 30Oct 2Oct 4Oct 8
32°FSep 23Sep 28Sep 30Oct 3Oct 6Oct 8Oct 10Oct 14Oct 18
28°FOct 1Oct 7Oct 11Oct 14Oct 17Oct 20Oct 23Oct 26Oct 30
24°FOct 14Oct 21Oct 24Oct 27Oct 30Nov 1Nov 3Nov 7Nov 13
20°FOct 29Nov 1Nov 3Nov 6Nov 9Nov 11Nov 15Nov 18Nov 23
16°FNov 4Nov 8Nov 12Nov 15Nov 17Nov 20Nov 23Nov 26Dec 1

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°F149142138135131127123119112
32°F168162158154151147144139133
28°F193186180176172167163159154
24°F218210205201197193188184176
20°F239231227222218214210205199
16°F256249244240236231227222215

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
7,831
Cooling degree days, base 65°F
495
Growing degree days, base 40°F
4,261
Growing degree days, base 45°F
3,262
Growing degree days, base 50°F
2,383
Growing degree days, base 55°F
1,621
Growing degree days, base 60°F
985

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,50800
February1,26600
March1,04509
April635248
May28927238
June71102482
July16184632
August32135569
September18342321
October548276
November91707
December1,32200

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 18 km from Iola. 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 USC00478951 (Waupaca). Public domain.