Dubuque County climate

Dubuque County Frost Dates and Growing Season

NOAA 1991-2020 normals for Dubuque Rgnl AP, 16.6 km from Dubuque County, elevation 1056 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Dubuque Rgnl AP. 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 11, a growing season of about 165 days.

Median at 36°F
last May 7, first October 2
Median at 32°F
last April 28, first October 11
Median at 28°F
last April 17, first October 21

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 21May 16May 13May 10May 7May 5May 2Apr 29Apr 23
32°FMay 12May 7May 4May 1Apr 28Apr 25Apr 21Apr 18Apr 13
28°FMay 3Apr 29Apr 24Apr 20Apr 17Apr 14Apr 10Apr 7Apr 2
24°FApr 22Apr 17Apr 12Apr 9Apr 6Apr 4Apr 1Mar 29Mar 21
20°FApr 12Apr 7Apr 3Apr 1Mar 28Mar 25Mar 20Mar 16Mar 11
16°FApr 3Mar 29Mar 24Mar 20Mar 17Mar 14Mar 11Mar 7Mar 3

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 27Sep 29Oct 2Oct 4Oct 7Oct 10Oct 14
32°FSep 28Oct 2Oct 5Oct 8Oct 11Oct 13Oct 16Oct 19Oct 23
28°FOct 8Oct 13Oct 16Oct 19Oct 21Oct 24Oct 26Oct 30Nov 2
24°FOct 17Oct 22Oct 25Oct 28Oct 31Nov 1Nov 4Nov 8Nov 13
20°FOct 27Nov 1Nov 3Nov 6Nov 9Nov 12Nov 15Nov 19Nov 25
16°FNov 5Nov 9Nov 12Nov 16Nov 19Nov 22Nov 25Nov 30Dec 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°F163158154150146143139135128
32°F186179174169165161157153146
28°F206200195191187182178173166
24°F227219214209206202198193184
20°F249241235231227223217213204
16°F267259254250245242237232225

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
7,084
Cooling degree days, base 65°F
638
Growing degree days, base 40°F
4,775
Growing degree days, base 45°F
3,700
Growing degree days, base 50°F
2,745
Growing degree days, base 55°F
1,912
Growing degree days, base 60°F
1,207

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,43200
February1,17701
March924118
April529378
May22938294
June37143556
July8217674
August18166614
September14263378
October4757117
November857014
December1,25501

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 16.6 km from Dubuque County. 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 USW00094908 (Dubuque Rgnl AP). Public domain.