Four Corners Frost Dates and Growing Season

NOAA 1991-2020 normals for Clermont 9 S, 15.6 km from Four Corners, elevation 130 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Clermont 9 S. 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 29 and the first fall freeze around January 11, a growing season of about 349 days.

Median at 36°F: last February 8, first January 2
Median at 32°F: last January 29, first January 11
Median at 28°F: last January 24, first January 19

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 9	Feb 28	Feb 21	Feb 14	Feb 8	Feb 3	Jan 29	Jan 20	Jan 9
32°F	Feb 26	Feb 14	Feb 8	Feb 2	Jan 29	Jan 23	Jan 16	Jan 9	Jan 2
28°F	Feb 11	Feb 6	Feb 1	Jan 28	Jan 24	Jan 19	Jan 12	Jan 8	Jan 1
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 5	Dec 15	Dec 23	Dec 29	Jan 2	Jan 6	Jan 12	Jan 21	Jan 31
32°F	Dec 21	Dec 30	Jan 4	Jan 8	Jan 11	Jan 18	Jan 26	Feb 1	Feb 8
28°F	Dec 28	Jan 4	Jan 8	Jan 12	Jan 19	Jan 24	Jan 29	Feb 2	Feb 8
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	357	343	334	327	319	311	304	296	283
32°F	365	365	365	358	349	341	334	325	313
28°F	365	365	365	365	365	365	365	349	333
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: 95% of years
32°F or colder: 66% of years
28°F or colder: 29% of years
24°F or colder: 9% of years
20°F or colder: 2% 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: 539
Cooling degree days, base 65°F: 3,711
Growing degree days, base 40°F: 12,298
Growing degree days, base 45°F: 10,481
Growing degree days, base 50°F: 8,681
Growing degree days, base 55°F: 6,925
Growing degree days, base 60°F: 5,254

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	186	53	349
February	112	67	382
March	58	134	542
April	8	248	690
May	0	411	876
June	0	517	968
July	0	583	1,048
August	0	583	1,048
September	0	514	965
October	5	361	822
November	40	155	564
December	130	85	428

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 15.6 km from Four Corners. 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 USC00081641 (Clermont 9 S). Public domain.