Park County Frost Dates and Growing Season

NOAA 1991-2020 normals for Antero Rsvr, 20.6 km from Park County, elevation 8939 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Antero Rsvr. 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 8

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	Jul 1	Jun 25	Jun 21	Jun 18	Jun 15	Jun 13	Jun 10	Jun 6	Jun 1
24°F	Jun 15	Jun 10	Jun 6	Jun 3	Jun 1	May 29	May 25	May 22	May 17
20°F	Jun 2	May 26	May 22	May 19	May 16	May 13	May 10	May 7	May 3
16°F	May 20	May 14	May 11	May 7	May 5	May 3	May 1	Apr 28	Apr 22

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	Aug 28	Sep 1	Sep 4	Sep 6	Sep 8	Sep 10	Sep 12	Sep 16	Sep 21
24°F	Sep 7	Sep 11	Sep 14	Sep 17	Sep 19	Sep 21	Sep 24	Sep 26	Sep 30
20°F	Sep 17	Sep 21	Sep 24	Sep 26	Sep 28	Oct 1	Oct 3	Oct 5	Oct 9
16°F	Sep 26	Sep 30	Oct 2	Oct 5	Oct 7	Oct 9	Oct 13	Oct 16	Oct 21

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	44	38	33	29	25	21	18	16	13
32°F	75	69	64	60	57	52	47	39	32
28°F	102	96	92	88	84	80	76	72	66
24°F	128	122	118	114	110	106	102	97	90
20°F	151	145	141	138	135	130	126	122	115
16°F	173	167	162	158	154	151	146	142	136

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: 10,756
Cooling degree days, base 65°F: 0
Growing degree days, base 40°F: 1,911
Growing degree days, base 45°F: 1,178
Growing degree days, base 50°F: 606
Growing degree days, base 55°F: 210
Growing degree days, base 60°F: 28

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Growing DD 50
January	1,592	0
February	1,364	0
March	1,208	0
April	935	0
May	679	12
June	380	106
July	216	251
August	279	191
September	494	44
October	865	1
November	1,185	0
December	1,562	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 20.6 km from Park 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 USC00050263 (Antero Rsvr). Public domain.