Alva Frost Dates and Growing Season

NOAA 1991-2020 normals for Ft Myers Sw Fl Rgnl AP, 24.7 km from Alva, elevation 31 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ft Myers Sw Fl Rgnl AP. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

A freeze (32°F or colder) happens in only 15 percent of years at Ft Myers Sw Fl Rgnl AP, so there is no typical freeze season.

Median at 36°F: last January 26, first January 14
Median at 32°F: last January 17, 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	Feb 16	Feb 7	Feb 4	Jan 31	Jan 26	Jan 19	Jan 13	Jan 9	Jan 3
32°F	Feb 6	Jan 31	Jan 29	Jan 23	Jan 17	Jan 13	Jan 10	Jan 7	Jan 6
28°F	–	–	–	–	–	–	–	–	–
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 29	Jan 3	Jan 7	Jan 10	Jan 14	Jan 21	Jan 27	Feb 2	Feb 10
32°F	Jan 4	Jan 7	Jan 9	Jan 11	Jan 16	Jan 21	Jan 27	Jan 31	Feb 5
28°F	–	–	–	–	–	–	–	–	–
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	365	365	365	365	363	353	340	331	319
32°F	365	365	365	365	365	365	365	365	350
28°F	365	365	365	365	365	365	365	365	365
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: 48% of years
32°F or colder: 15% of years
28°F or colder: 3% of years
24°F or colder: 0% 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: 268
Cooling degree days, base 65°F: 3,933
Growing degree days, base 40°F: 12,790
Growing degree days, base 45°F: 10,966
Growing degree days, base 50°F: 9,146
Growing degree days, base 55°F: 7,342
Growing degree days, base 60°F: 5,587

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	101	87	455
February	56	105	469
March	26	166	605
April	4	275	722
May	0	403	868
June	0	499	950
July	0	549	1,014
August	0	575	1,040
September	0	520	971
October	2	398	862
November	14	221	657
December	65	134	535

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 24.7 km from Alva. 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 USW00012894 (Ft Myers Sw Fl Rgnl AP). Public domain.