Jefferson climate

Jefferson Frost Dates and Growing Season

NOAA 1991-2020 normals for New Orleans Audubon, 5.9 km from Jefferson, elevation 20 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for New Orleans Audubon. 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 January 24 and the first fall freeze around January 2, a growing season of about 341 days.

Median at 36°F
last February 6, first December 16
Median at 32°F
last January 24, first January 2
Median at 28°F
last January 15, first January 8

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°FMar 7Feb 28Feb 22Feb 14Feb 6Feb 2Jan 28Jan 22Jan 11
32°FFeb 23Feb 9Feb 2Jan 28Jan 24Jan 19Jan 14Jan 6Dec 28
28°FFeb 8Jan 31Jan 24Jan 19Jan 15Jan 11Jan 7Jan 3Dec 29
24°FFeb 10Feb 1Jan 27Jan 22Jan 16Jan 13Jan 9Jan 5Jan 2
20°F–––––––––
16°F–––––––––

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°FNov 19Nov 29Dec 5Dec 10Dec 16Dec 23Dec 30Jan 5Jan 15
32°FDec 5Dec 14Dec 23Dec 30Jan 2Jan 6Jan 11Jan 18Feb 1
28°FDec 22Dec 31Jan 2Jan 5Jan 8Jan 12Jan 17Jan 24Feb 1
24°FJan 1Jan 3Jan 6Jan 11Jan 14Jan 17Jan 22Feb 1Feb 10
20°F–––––––––
16°F–––––––––

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°F342333324316308301295286275
32°F365365357348341334329320309
28°F365365365365365365358347335
24°F365365365365365365365365361
20°F365365365365365365365365365
16°F365365365365365365365365365

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
98% of years
32°F or colder
76% of years
28°F or colder
36% of years
24°F or colder
10% of years
20°F or colder
2% of years
16°F or colder
0% 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
1,019
Cooling degree days, base 65°F
3,518
Growing degree days, base 40°F
11,632
Growing degree days, base 45°F
9,831
Growing degree days, base 50°F
8,076
Growing degree days, base 55°F
6,412
Growing degree days, base 60°F
4,885

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January31619216
February19438280
March9397473
April19212644
May1422887
June05611,011
July06281,093
August06341,099
September0506955
October15283733
November12385418
December25933267

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 5.9 km from Jefferson. 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 USW00012930 (New Orleans Audubon). Public domain.