Telluride Frost Dates and Growing Season

NOAA 1991-2020 normals for Telluride 4WNW, 5.5 km from Telluride, elevation 8646 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Telluride 4WNW. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

NOAA does not state freeze dates for this station.

Median at 28°F: last June 15, first September 16

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	–	–	–	–	–	–	–	–	–
32°F	–	–	–	–	–	–	–	–	–
28°F	Jun 30	Jun 24	Jun 21	Jun 18	Jun 15	Jun 12	Jun 8	Jun 5	May 31
24°F	Jun 12	Jun 7	Jun 3	May 31	May 26	May 22	May 19	May 16	May 10
20°F	May 20	May 17	May 13	May 10	May 7	May 4	May 2	Apr 29	Apr 24
16°F	May 8	May 3	Apr 30	Apr 27	Apr 24	Apr 21	Apr 17	Apr 13	Apr 8

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	–	–	–	–	–	–	–	–	–
32°F	–	–	–	–	–	–	–	–	–
28°F	Sep 2	Sep 6	Sep 10	Sep 13	Sep 16	Sep 18	Sep 22	Sep 25	Sep 29
24°F	Sep 14	Sep 19	Sep 23	Sep 25	Sep 27	Sep 30	Oct 1	Oct 5	Oct 8
20°F	Sep 24	Sep 28	Oct 1	Oct 4	Oct 6	Oct 8	Oct 11	Oct 15	Oct 20
16°F	Oct 2	Oct 6	Oct 10	Oct 13	Oct 16	Oct 19	Oct 23	Oct 26	Nov 1

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	46	39	34	30	26	24	21	18	15
32°F	79	72	68	64	60	55	50	44	36
28°F	110	104	100	95	91	87	83	76	69
24°F	141	134	130	126	122	118	114	108	100
20°F	169	162	158	154	150	146	142	137	131
16°F	194	188	183	179	175	170	165	160	153

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: 100% of years
28°F or colder: 100% of years
24°F or colder: 100% of years
20°F or colder: 100% of years
16°F or colder: 100% 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: 9,781
Cooling degree days, base 65°F: 1
Growing degree days, base 40°F: 2,166
Growing degree days, base 45°F: 1,365
Growing degree days, base 50°F: 728
Growing degree days, base 55°F: 270
Growing degree days, base 60°F: 46

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	1,449	0	0
February	1,219	0	0
March	1,138	0	0
April	858	0	1
May	632	0	20
June	350	0	130
July	196	1	270
August	244	0	223
September	426	0	80
October	763	0	5
November	1,080	0	0
December	1,426	0	0

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 5.5 km from Telluride. 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 USC00058204 (Telluride 4WNW). Public domain.