Mesa Verde Frost Dates and Growing Season

NOAA 1991-2020 normals for Blythe AP, 2.1 km from Mesa Verde, elevation 395 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Blythe AP. 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 5 and the first fall freeze around December 21, a growing season of about 347 days.

Median at 36°F: last February 6, first December 7
Median at 32°F: last January 5, first December 21
Median at 28°F: last December 31, first December 30

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 2	Feb 23	Feb 16	Feb 11	Feb 6	Jan 31	Jan 24	Jan 13	Jan 3
32°F	Feb 18	Feb 3	Jan 26	Jan 12	Jan 5	Dec 31	Dec 27	Dec 23	Dec 15
28°F	Feb 12	Jan 25	Jan 11	Jan 4	Dec 31	Dec 28	Dec 24	Dec 19	Dec 9
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 22	Nov 27	Dec 1	Dec 4	Dec 7	Dec 10	Dec 14	Dec 18	Dec 25
32°F	Dec 2	Dec 8	Dec 13	Dec 17	Dec 21	Dec 24	Dec 28	Jan 2	Jan 18
28°F	Dec 8	Dec 17	Dec 21	Dec 26	Dec 30	Dec 31	Jan 6	Jan 20	Feb 4
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	337	328	320	311	305	298	291	284	274
32°F	365	365	359	353	347	341	334	327	312
28°F	365	365	365	365	365	365	365	362	347
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: 80% of years
28°F or colder: 25% of years
24°F or colder: 1% 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: 1,011
Cooling degree days, base 65°F: 4,460
Growing degree days, base 40°F: 12,575
Growing degree days, base 45°F: 10,753
Growing degree days, base 50°F: 8,958
Growing degree days, base 55°F: 7,264
Growing degree days, base 60°F: 5,756

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	290	1	188
February	173	12	262
March	71	90	484
April	14	229	665
May	1	477	941
June	0	726	1,176
July	0	930	1,395
August	0	921	1,386
September	0	690	1,140
October	7	331	789
November	116	54	390
December	340	1	143

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 2.1 km from Mesa Verde. 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 USW00023158 (Blythe AP). Public domain.