Ehrenberg Frost Dates and Growing Season

NOAA 1991-2020 normals for Ehrenberg 2 E, 5.1 km from Ehrenberg, elevation 465 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ehrenberg 2 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 January 4 and the first fall freeze around December 19, a growing season of about 347 days.

Median at 36°F: last February 3, first December 7
Median at 32°F: last January 4, first December 19
Median at 28°F: last December 29, first December 26

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 28	Feb 20	Feb 15	Feb 8	Feb 3	Jan 31	Jan 24	Jan 15	Jan 5
32°F	Feb 10	Jan 27	Jan 15	Jan 8	Jan 4	Dec 31	Dec 28	Dec 23	Dec 16
28°F	Feb 4	Jan 8	Jan 3	Dec 31	Dec 29	Dec 26	Dec 22	Dec 18	Dec 13
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	Nov 25	Nov 29	Dec 2	Dec 5	Dec 7	Dec 11	Dec 14	Dec 18	Dec 22
32°F	Dec 5	Dec 9	Dec 12	Dec 16	Dec 19	Dec 22	Dec 26	Dec 30	Jan 5
28°F	Dec 11	Dec 15	Dec 20	Dec 23	Dec 26	Dec 29	Dec 31	Jan 4	Jan 13
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	338	327	319	312	305	298	292	285	276
32°F	365	362	357	351	347	342	337	331	315
28°F	365	365	365	365	365	365	364	359	350
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: 100% of years
32°F or colder: 83% of years
28°F or colder: 29% of years
24°F or colder: 3% 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: 1,079
Cooling degree days, base 65°F: 4,356
Growing degree days, base 40°F: 12,402
Growing degree days, base 45°F: 10,582
Growing degree days, base 50°F: 8,795
Growing degree days, base 55°F: 7,122
Growing degree days, base 60°F: 5,637

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	304	1	175
February	183	8	248
March	81	72	456
April	19	205	636
May	2	465	929
June	0	723	1,173
July	0	907	1,372
August	0	902	1,367
September	0	687	1,137
October	5	334	794
November	119	51	385
December	366	1	124

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 5.1 km from Ehrenberg. 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 USC00022790 (Ehrenberg 2 E). Public domain.