Riviera Frost Dates and Growing Season

NOAA 1991-2020 normals for Sarita 7 E, 14.9 km from Riviera, elevation 38 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Sarita 7 E. 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 17 and the first fall freeze around December 8, a growing season of about 300 days.

Median at 36°F: last March 2, first November 26
Median at 32°F: last February 17, first December 8
Median at 28°F: last January 28, first December 28

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 24	Mar 15	Mar 11	Mar 6	Mar 2	Feb 27	Feb 22	Feb 15	Feb 6
32°F	Mar 13	Mar 6	Feb 28	Feb 23	Feb 17	Feb 10	Feb 2	Jan 26	Jan 16
28°F	Mar 7	Feb 24	Feb 12	Feb 3	Jan 28	Jan 21	Jan 11	Jan 2	Dec 19
24°F	Mar 1	Feb 14	Feb 2	Jan 22	Jan 13	Jan 5	Dec 31	Dec 23	Dec 14
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	Nov 9	Nov 14	Nov 18	Nov 22	Nov 26	Nov 29	Dec 3	Dec 9	Dec 22
32°F	Nov 19	Nov 25	Nov 29	Dec 3	Dec 8	Dec 14	Dec 24	Jan 2	Jan 16
28°F	Nov 30	Dec 6	Dec 12	Dec 20	Dec 28	Jan 2	Jan 11	Jan 20	Feb 4
24°F	Dec 9	Dec 16	Dec 23	Dec 31	Jan 3	Jan 9	Jan 20	Feb 4	Feb 24
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	303	290	283	275	269	263	258	250	240
32°F	337	325	315	307	300	293	284	274	263
28°F	365	365	353	342	334	327	317	306	293
24°F	365	365	365	365	365	365	355	342	329
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: 100% of years
32°F or colder: 98% of years
28°F or colder: 82% of years
24°F or colder: 39% of years
20°F or colder: 6% 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: 903
Cooling degree days, base 65°F: 3,507
Growing degree days, base 40°F: 11,738
Growing degree days, base 45°F: 9,939
Growing degree days, base 50°F: 8,185
Growing degree days, base 55°F: 6,508
Growing degree days, base 60°F: 4,940

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	285	33	256
February	166	62	336
March	83	128	513
April	18	249	682
May	1	426	890
June	0	509	959
July	0	583	1,048
August	0	600	1,065
September	0	459	909
October	9	300	756
November	91	111	475
December	250	48	298

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 14.9 km from Riviera. 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 USC00418081 (Sarita 7 E). Public domain.