Palm Valley Frost Dates and Growing Season

NOAA 1991-2020 normals for Jacksonville Beach, 12.2 km from Palm Valley, elevation 10 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Jacksonville Beach. 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 31 and the first fall freeze around January 10, a growing season of about 345 days.

Median at 36°F: last February 9, first January 1
Median at 32°F: last January 31, first January 10
Median at 28°F: last January 24, first January 16

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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	Mar 10	Mar 2	Feb 25	Feb 16	Feb 9	Feb 3	Jan 30	Jan 21	Jan 10
32°F	Mar 2	Feb 21	Feb 11	Feb 3	Jan 31	Jan 24	Jan 17	Jan 11	Jan 1
28°F	Feb 16	Feb 6	Jan 31	Jan 28	Jan 24	Jan 16	Jan 11	Jan 4	Dec 27
24°F	–	–	–	–	–	–	–	–	–
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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	Dec 2	Dec 8	Dec 18	Dec 26	Jan 1	Jan 5	Jan 11	Jan 17	Jan 29
32°F	Dec 16	Dec 25	Jan 1	Jan 6	Jan 10	Jan 16	Jan 24	Jan 31	Feb 14
28°F	Dec 22	Dec 31	Jan 5	Jan 10	Jan 16	Jan 22	Jan 28	Jan 31	Feb 9
24°F	–	–	–	–	–	–	–	–	–
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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	352	338	332	325	318	309	303	295	284
32°F	365	365	364	354	345	337	331	317	306
28°F	365	365	365	365	365	365	363	349	334
24°F	365	365	365	365	365	365	365	365	365
20°F	365	365	365	365	365	365	365	365	365
16°F	365	365	365	365	365	365	365	365	365

How often it gets that cold

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

36°F or colder: 94% of years
32°F or colder: 67% of years
28°F or colder: 28% of years
24°F or colder: 5% of years
20°F or colder: 0% 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: 829
Cooling degree days, base 65°F: 3,196
Growing degree days, base 40°F: 11,496
Growing degree days, base 45°F: 9,684
Growing degree days, base 50°F: 7,903
Growing degree days, base 55°F: 6,197
Growing degree days, base 60°F: 4,616

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	267	21	248
February	177	31	285
March	92	81	457
April	19	176	608
May	1	360	825
June	0	482	932
July	0	556	1,021
August	0	552	1,017
September	0	472	922
October	8	309	766
November	72	113	492
December	193	43	330

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 12.2 km from Palm Valley. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00084366 (Jacksonville Beach). Public domain.