Dubuque climate

Dubuque Frost Dates and Growing Season

NOAA 1991-2020 normals for Dubuque L&d 11, 4.6 km from Dubuque, elevation 620 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Dubuque L&d 11. 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 19 and the first fall freeze around October 21, a growing season of about 184 days.

Median at 36°F
last May 1, first October 12
Median at 32°F
last April 19, first October 21
Median at 28°F
last April 7, 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 14May 8May 6May 3May 1Apr 29Apr 25Apr 20Apr 16
32°FMay 4Apr 30Apr 25Apr 22Apr 19Apr 16Apr 12Apr 9Apr 4
28°FApr 22Apr 17Apr 13Apr 10Apr 7Apr 5Apr 3Apr 1Mar 25
24°FApr 12Apr 7Apr 4Apr 2Mar 31Mar 28Mar 24Mar 19Mar 14
20°FApr 4Apr 1Mar 28Mar 24Mar 21Mar 18Mar 15Mar 12Mar 7
16°FMar 30Mar 24Mar 20Mar 17Mar 14Mar 11Mar 9Mar 5Mar 2

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 29Oct 3Oct 7Oct 10Oct 12Oct 15Oct 17Oct 21Oct 24
32°FOct 7Oct 13Oct 16Oct 19Oct 21Oct 24Oct 27Oct 30Nov 2
28°FOct 19Oct 23Oct 27Oct 30Nov 1Nov 2Nov 5Nov 9Nov 14
24°FOct 29Nov 1Nov 3Nov 6Nov 10Nov 13Nov 16Nov 20Nov 24
20°FNov 4Nov 9Nov 13Nov 17Nov 19Nov 22Nov 25Nov 30Dec 3
16°FNov 11Nov 18Nov 21Nov 25Nov 28Nov 30Dec 2Dec 7Dec 13

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°F182175170166163160156151144
32°F203197193189184180175171164
28°F226218213209205201197192185
24°F245238233228223219215211205
20°F263256251246242237233227220
16°F278271267262258255249244235

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
6,885
Cooling degree days, base 65°F
863
Growing degree days, base 40°F
5,145
Growing degree days, base 45°F
4,055
Growing degree days, base 50°F
3,078
Growing degree days, base 55°F
2,218
Growing degree days, base 60°F
1,478

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,43200
February1,18600
March929116
April513385
May20250327
June25187612
July3292755
August8231688
September10489438
October4269141
November827015
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 4.6 km from Dubuque. 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 USC00132364 (Dubuque L&d 11). Public domain.