Polk County climate

Polk County Frost Dates and Growing Season

NOAA 1991-2020 normals for Bolivar 1 Ne, 0.8 km from Polk County, elevation 987 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Bolivar 1 Ne. 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 14 and the first fall freeze around October 23, a growing season of about 188 days.

Median at 36°F
last April 27, first October 13
Median at 32°F
last April 14, first October 23
Median at 28°F
last April 1, 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 12May 7May 3Apr 30Apr 27Apr 23Apr 20Apr 15Apr 10
32°FMay 2Apr 26Apr 21Apr 18Apr 14Apr 11Apr 7Apr 2Mar 29
28°FApr 18Apr 12Apr 8Apr 4Apr 1Mar 30Mar 27Mar 22Mar 17
24°FApr 7Apr 3Mar 29Mar 26Mar 23Mar 19Mar 14Mar 9Mar 3
20°FMar 29Mar 22Mar 18Mar 13Mar 9Mar 5Mar 2Feb 26Feb 21
16°FMar 18Mar 12Mar 7Mar 4Mar 1Feb 25Feb 21Feb 15Feb 5

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

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°F188181176172167163160155147
32°F211202197192188184179173166
28°F234227221216211207202197190
24°F259251244239234228222217209
20°F282273267261257252246239230
16°F305295289283277272266261251

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
4,630
Cooling degree days, base 65°F
1,366
Growing degree days, base 40°F
6,651
Growing degree days, base 45°F
5,310
Growing degree days, base 50°F
4,114
Growing degree days, base 55°F
3,057
Growing degree days, base 60°F
2,139

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,01507
February794019
March601480
April30622221
May100101469
June8268709
July1405869
August2367831
September52166565
October27330260
November582370
December897014

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 0.8 km from Polk 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 USC00230789 (Bolivar 1 Ne). Public domain.