Oppelo climate

Oppelo Frost Dates and Growing Season

NOAA 1991-2020 normals for Morrilton, 6.3 km from Oppelo, elevation 340 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Morrilton. 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 March 30 and the first fall freeze around November 2, a growing season of about 219 days.

Median at 36°F
last April 10, first October 24
Median at 32°F
last March 30, first November 2
Median at 28°F
last March 14, first November 14

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°FApr 27Apr 21Apr 17Apr 13Apr 10Apr 8Apr 5Apr 1Mar 28
32°FApr 15Apr 9Apr 5Apr 2Mar 30Mar 26Mar 21Mar 16Mar 11
28°FApr 2Mar 28Mar 23Mar 18Mar 14Mar 10Mar 7Mar 3Feb 26
24°FMar 19Mar 13Mar 8Mar 4Mar 1Feb 27Feb 22Feb 16Feb 7
20°FMar 7Mar 1Feb 25Feb 20Feb 14Feb 8Feb 2Jan 28Jan 18
16°FFeb 27Feb 15Feb 7Feb 2Jan 29Jan 22Jan 15Jan 6Dec 30

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°FOct 11Oct 16Oct 19Oct 21Oct 24Oct 27Oct 30Nov 1Nov 6
32°FOct 19Oct 24Oct 28Nov 1Nov 2Nov 5Nov 8Nov 13Nov 20
28°FOct 30Nov 3Nov 7Nov 10Nov 14Nov 18Nov 23Nov 27Dec 2
24°FNov 8Nov 14Nov 20Nov 24Nov 28Dec 1Dec 5Dec 10Dec 19
20°FNov 20Nov 28Dec 2Dec 9Dec 14Dec 20Dec 25Jan 1Jan 8
16°FDec 3Dec 12Dec 20Dec 26Dec 31Jan 3Jan 10Jan 17Feb 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°F217210204199196191187182175
32°F245236229223219214208203195
28°F270261255251245240233227217
24°F299289283277271265260254245
20°F334324316308302295288279268
16°F365359349340334329321313302

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
99% of years
16°F or colder
86% 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
3,359
Cooling degree days, base 65°F
1,955
Growing degree days, base 40°F
8,021
Growing degree days, base 45°F
6,505
Growing degree days, base 50°F
5,141
Growing degree days, base 55°F
3,931
Growing degree days, base 60°F
2,866

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January789022
February603141
March4229144
April17944329
May40170596
June1385834
July0518983
August0487952
September14268704
October15866384
November4388122
December715133

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 6.3 km from Oppelo. 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 USC00034938 (Morrilton). Public domain.