Lake County Frost Dates and Growing Season

NOAA 1991-2020 normals for Leadville Lake CO AP, 3.9 km from Lake County, elevation 9933 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Leadville Lake CO AP. 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 12, first September 10

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 23	Jun 19	Jun 16	Jun 12	Jun 9	Jun 6	Jun 3	May 31
24°F	Jun 9	Jun 4	Jun 1	May 29	May 26	May 23	May 20	May 17	May 12
20°F	May 28	May 22	May 17	May 14	May 12	May 9	May 6	May 4	Apr 30
16°F	May 15	May 10	May 7	May 4	May 2	Apr 30	Apr 28	Apr 24	Apr 19

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 30	Sep 3	Sep 5	Sep 8	Sep 10	Sep 13	Sep 15	Sep 18	Sep 23
24°F	Sep 9	Sep 15	Sep 18	Sep 21	Sep 23	Sep 26	Sep 29	Oct 1	Oct 5
20°F	Sep 21	Sep 26	Sep 29	Oct 2	Oct 4	Oct 6	Oct 10	Oct 13	Oct 18
16°F	Sep 28	Oct 3	Oct 7	Oct 10	Oct 13	Oct 17	Oct 19	Oct 23	Oct 28

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	33	27	24	21	19	16	14	12	10
32°F	73	66	61	56	52	47	41	36	29
28°F	107	100	96	92	88	85	80	75	68
24°F	138	131	127	122	119	114	110	106	99
20°F	163	156	152	148	144	141	136	131	124
16°F	182	176	171	167	164	160	155	151	144

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: 11,061
Cooling degree days, base 65°F: 0
Growing degree days, base 40°F: 1,531
Growing degree days, base 45°F: 852
Growing degree days, base 50°F: 350
Growing degree days, base 55°F: 68
Growing degree days, base 60°F: 2

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Growing DD 50
January	1,487	0
February	1,312	0
March	1,252	0
April	1,018	0
May	749	5
June	447	58
July	307	162
August	369	108
September	554	17
October	876	0
November	1,206	0
December	1,485	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 3.9 km from Lake 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 USW00093009 (Leadville Lake CO AP). Public domain.