River Park Frost Dates and Growing Season

NOAA 1991-2020 normals for Ft Pierce, 14.2 km from River Park, elevation 25 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ft Pierce. 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 33 percent of years at Ft Pierce, so there is no typical freeze season.

Median at 36°F: last January 31, first January 8
Median at 32°F: last January 22, first January 12

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 7	Feb 22	Feb 10	Feb 3	Jan 31	Jan 21	Jan 14	Jan 6	Dec 29
32°F	Feb 27	Feb 9	Feb 2	Jan 29	Jan 22	Jan 13	Jan 9	Jan 3	Dec 26
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 14	Dec 23	Dec 28	Jan 2	Jan 8	Jan 14	Jan 24	Feb 1	Feb 13
32°F	Dec 20	Dec 29	Jan 2	Jan 6	Jan 12	Jan 19	Jan 28	Feb 2	Feb 12
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	354	344	334	327	315	304
32°F	365	365	365	365	365	365	361	347	330
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: 69% of years
32°F or colder: 33% of years
28°F or colder: 8% 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: 405
Cooling degree days, base 65°F: 3,502
Growing degree days, base 40°F: 12,223
Growing degree days, base 45°F: 10,401
Growing degree days, base 50°F: 8,589
Growing degree days, base 55°F: 6,807
Growing degree days, base 60°F: 5,094

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	136	65	402
February	85	81	419
March	52	137	551
April	9	229	671
May	0	363	828
June	0	457	908
July	0	516	981
August	0	524	989
September	0	473	923
October	3	366	828
November	27	184	608
December	93	107	484

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 14.2 km from River Park. 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 USC00083207 (Ft Pierce). Public domain.