Teller County Frost Dates and Growing Season

NOAA 1991-2020 normals for Florissant Fossil Bed, 11.2 km from Teller County, elevation 8402 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Florissant Fossil Bed. 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 5, first September 14

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 25	Jun 17	Jun 12	Jun 8	Jun 5	Jun 3	May 31	May 28	May 24
24°F	Jun 3	May 31	May 27	May 24	May 22	May 19	May 16	May 14	May 9
20°F	May 23	May 18	May 15	May 12	May 10	May 7	May 5	May 2	Apr 27
16°F	May 15	May 9	May 5	May 2	Apr 30	Apr 27	Apr 24	Apr 19	Apr 14

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 9	Sep 12	Sep 14	Sep 17	Sep 19	Sep 23	Sep 27
24°F	Sep 14	Sep 18	Sep 21	Sep 23	Sep 25	Sep 28	Sep 30	Oct 2	Oct 6
20°F	Sep 24	Sep 27	Oct 1	Oct 2	Oct 4	Oct 7	Oct 9	Oct 13	Oct 18
16°F	Sep 30	Oct 3	Oct 7	Oct 10	Oct 13	Oct 16	Oct 18	Oct 21	Oct 26

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	58	51	46	40	37	32	28	24	19
32°F	91	84	77	73	68	64	58	52	44
28°F	117	111	107	103	99	95	91	87	78
24°F	141	136	132	128	125	122	119	115	108
20°F	164	159	154	150	147	143	140	135	130
16°F	187	180	175	170	166	163	158	152	145

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: 8,972
Cooling degree days, base 65°F: 3
Growing degree days, base 40°F: 2,445
Growing degree days, base 45°F: 1,585
Growing degree days, base 50°F: 896
Growing degree days, base 55°F: 381
Growing degree days, base 60°F: 78

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	1,322	0	0
February	1,137	0	0
March	1,018	0	0
April	800	0	3
May	570	0	34
June	278	1	182
July	151	2	316
August	210	0	257
September	392	0	98
October	733	0	6
November	1,029	0	0
December	1,333	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 11.2 km from Teller County. 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 USC00052965 (Florissant Fossil Bed). Public domain.