Jones County climate

Jones County Frost Dates and Growing Season

NOAA 1991-2020 normals for Anamosa 1 Wnw, 13.4 km from Jones County, elevation 805 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Anamosa 1 Wnw. 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 1 and the first fall freeze around October 4, a growing season of about 154 days.

Median at 36°F
last May 13, first September 27
Median at 32°F
last May 1, first October 4
Median at 28°F
last April 21, first October 16

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 28May 23May 19May 16May 13May 10May 7May 2Apr 28
32°FMay 18May 12May 9May 5May 1Apr 29Apr 27Apr 23Apr 18
28°FMay 6May 1Apr 28Apr 25Apr 21Apr 18Apr 16Apr 12Apr 6
24°FApr 26Apr 20Apr 16Apr 13Apr 10Apr 7Apr 4Apr 1Mar 26
20°FApr 15Apr 10Apr 6Apr 4Apr 1Mar 30Mar 26Mar 22Mar 15
16°FApr 7Apr 2Mar 30Mar 25Mar 21Mar 18Mar 14Mar 10Mar 4

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 18Sep 21Sep 24Sep 27Sep 29Oct 2Oct 4Oct 8
32°FSep 21Sep 26Sep 29Oct 2Oct 4Oct 7Oct 10Oct 14Oct 18
28°FOct 1Oct 6Oct 10Oct 13Oct 16Oct 19Oct 22Oct 25Oct 30
24°FOct 11Oct 17Oct 21Oct 24Oct 27Oct 30Nov 1Nov 3Nov 9
20°FOct 23Oct 27Oct 31Nov 2Nov 4Nov 7Nov 10Nov 15Nov 21
16°FNov 1Nov 4Nov 7Nov 11Nov 14Nov 18Nov 22Nov 25Dec 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°F156149144141137132128123116
32°F173168163158154151147141134
28°F196188183180175171167162155
24°F217210205200197193188182175
20°F241232227221217213209204197
16°F261254249243238234229223216

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
7,183
Cooling degree days, base 65°F
672
Growing degree days, base 40°F
4,785
Growing degree days, base 45°F
3,716
Growing degree days, base 50°F
2,766
Growing degree days, base 55°F
1,939
Growing degree days, base 60°F
1,237

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,46100
February1,20500
March935015
April529480
May23337291
June36153567
July7233691
August21177621
September14760371
October4848115
November871012
December1,25402

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 13.4 km from Jones 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 USC00130213 (Anamosa 1 Wnw). Public domain.