Johnston County climate

Johnston County Frost Dates and Growing Season

NOAA 1991-2020 normals for Tishomingo 6N Mesonet, 2.4 km from Johnston County, elevation 879 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Tishomingo 6N Mesonet. 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 29 and the first fall freeze around November 5, a growing season of about 222 days.

Median at 36°F
last April 8, first October 27
Median at 32°F
last March 29, first November 5
Median at 28°F
last March 13, 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 26Apr 20Apr 16Apr 12Apr 8Apr 6Apr 3Mar 29Mar 23
32°FApr 16Apr 8Apr 4Apr 1Mar 29Mar 24Mar 20Mar 15Mar 9
28°FApr 3Mar 28Mar 22Mar 17Mar 13Mar 9Mar 5Feb 28Feb 24
24°FMar 19Mar 13Mar 8Mar 5Mar 1Feb 27Feb 22Feb 15Feb 6
20°FMar 9Mar 3Feb 28Feb 23Feb 17Feb 9Feb 3Jan 28Jan 17
16°FMar 1Feb 21Feb 12Feb 4Jan 30Jan 24Jan 16Jan 6Dec 27

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 15Oct 19Oct 21Oct 24Oct 27Oct 30Nov 1Nov 5Nov 10
32°FOct 21Oct 26Oct 30Nov 2Nov 5Nov 8Nov 12Nov 15Nov 21
28°FOct 29Nov 4Nov 7Nov 11Nov 14Nov 18Nov 23Nov 28Dec 3
24°FNov 7Nov 13Nov 18Nov 24Nov 28Dec 1Dec 4Dec 8Dec 15
20°FNov 19Nov 27Dec 1Dec 6Dec 11Dec 17Dec 23Dec 30Jan 8
16°FDec 2Dec 8Dec 15Dec 22Dec 27Jan 2Jan 7Jan 16Jan 30

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°F224215209204200195191186179
32°F248238231227222217212206197
28°F272263257251245240234228219
24°F302291283277271265259252244
20°F334322314307301294287277267
16°F365357347338332325317307297

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
85% 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
3,126
Cooling degree days, base 65°F
2,033
Growing degree days, base 40°F
8,290
Growing degree days, base 45°F
6,735
Growing degree days, base 50°F
5,322
Growing degree days, base 55°F
4,069
Growing degree days, base 60°F
2,970

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January742023
February555266
March36813181
April16540338
May41167591
June0390840
July0522987
August0519984
September9293733
October14778406
November4078141
December692134

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 2.4 km from Johnston County. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00348900 (Tishomingo 6N Mesonet). Public domain.