Chalmette climate

Chalmette Frost Dates and Growing Season

NOAA 1991-2020 normals for Chalmette, 2.1 km from Chalmette, elevation 3 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Chalmette. 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 February 10 and the first fall freeze around December 17, a growing season of about 309 days.

Median at 36°F
last February 26, first November 29
Median at 32°F
last February 10, first December 17
Median at 28°F
last January 26, first January 2

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 17Mar 12Mar 6Mar 1Feb 26Feb 21Feb 15Feb 7Jan 30
32°FMar 8Feb 28Feb 23Feb 16Feb 10Feb 3Jan 31Jan 24Jan 12
28°FFeb 21Feb 11Feb 4Jan 31Jan 26Jan 20Jan 14Jan 8Dec 31
24°FFeb 11Feb 3Jan 30Jan 23Jan 18Jan 13Jan 8Jan 3Dec 28
20°FFeb 10Feb 3Jan 30Jan 24Jan 18Jan 13Jan 9Jan 5Jan 2
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 10Nov 16Nov 21Nov 25Nov 29Dec 2Dec 6Dec 13Dec 26
32°FNov 21Nov 29Dec 3Dec 9Dec 17Dec 27Jan 1Jan 5Jan 14
28°FDec 4Dec 15Dec 25Dec 31Jan 2Jan 7Jan 11Jan 17Jan 30
24°FDec 20Dec 30Jan 1Jan 5Jan 9Jan 12Jan 19Jan 30Feb 7
20°FJan 1Jan 2Jan 7Jan 10Jan 16Jan 21Jan 28Feb 1Feb 10
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°F311299291283277270265258249
32°F343332323316309304296286273
28°F365365356348340334329320308
24°F365365365365365364353342331
20°F365365365365365365365365362
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
100% of years
32°F or colder
98% of years
28°F or colder
80% of years
24°F or colder
42% of years
20°F or colder
13% of years
16°F or colder
2% 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
1,289
Cooling degree days, base 65°F
3,111
Growing degree days, base 40°F
10,966
Growing degree days, base 45°F
9,178
Growing degree days, base 50°F
7,457
Growing degree days, base 55°F
5,850
Growing degree days, base 60°F
4,398

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January39111162
February2537196
March14167398
April18163595
May0375840
June0528977
July05801,045
August05931,058
September0463913
October13249700
November15460366
December31917207

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 2.1 km from Chalmette. 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 USC00166130 (Chalmette). Public domain.