Garnavillo climate

Garnavillo Frost Dates and Growing Season

NOAA 1991-2020 normals for Guttenberg L&d 10, 14.7 km from Garnavillo, elevation 618 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Guttenberg L&d 10. 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 21 and the first fall freeze around October 18, a growing season of about 178 days.

Median at 36°F
last May 3, first October 7
Median at 32°F
last April 21, first October 18
Median at 28°F
last April 9, first October 27

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 16May 12May 8May 5May 3Apr 30Apr 28Apr 23Apr 18
32°FMay 6May 2Apr 30Apr 25Apr 21Apr 19Apr 15Apr 11Apr 7
28°FApr 26Apr 21Apr 17Apr 13Apr 9Apr 7Apr 5Apr 2Mar 30
24°FApr 15Apr 9Apr 5Apr 3Apr 1Mar 30Mar 26Mar 21Mar 15
20°FApr 5Apr 1Mar 29Mar 26Mar 22Mar 19Mar 16Mar 12Mar 7
16°FMar 29Mar 24Mar 21Mar 18Mar 15Mar 12Mar 8Mar 5Mar 1

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 29Oct 2Oct 5Oct 7Oct 10Oct 12Oct 16Oct 21
32°FOct 4Oct 9Oct 12Oct 15Oct 18Oct 20Oct 23Oct 26Oct 30
28°FOct 14Oct 20Oct 22Oct 25Oct 27Oct 29Nov 1Nov 3Nov 8
24°FOct 24Oct 29Nov 1Nov 3Nov 5Nov 8Nov 11Nov 14Nov 19
20°FNov 2Nov 6Nov 10Nov 12Nov 15Nov 18Nov 21Nov 24Nov 30
16°FNov 10Nov 14Nov 18Nov 20Nov 23Nov 26Nov 30Dec 3Dec 9

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°F174168163160156152148143138
32°F196190186183178174170165158
28°F218211207203199195191186179
24°F239232228223219215211206200
20°F259253248244239235230224217
16°F275268262258254250245240232

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
6,796
Cooling degree days, base 65°F
832
Growing degree days, base 40°F
5,154
Growing degree days, base 45°F
4,053
Growing degree days, base 50°F
3,064
Growing degree days, base 55°F
2,195
Growing degree days, base 60°F
1,449

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,42300
February1,16500
March902119
April485597
May19151336
June25183607
July3281742
August9217673
September11085430
October43010141
November824018
December1,23101

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 14.7 km from Garnavillo. 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 USC00133517 (Guttenberg L&d 10). Public domain.