Summit County Frost Dates and Growing Season

NOAA 1991-2020 normals for Coalville 13 E, 17.9 km from Summit County, elevation 6510 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Coalville 13 E. 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 19, first September 9

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 3	Jun 29	Jun 25	Jun 22	Jun 19	Jun 16	Jun 14	Jun 10	Jun 5
24°F	Jun 20	Jun 15	Jun 11	Jun 7	Jun 3	Jun 1	May 26	May 21	May 14
20°F	Jun 6	May 28	May 21	May 16	May 13	May 10	May 5	May 2	Apr 26
16°F	May 14	May 7	May 2	Apr 29	Apr 25	Apr 21	Apr 18	Apr 14	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	Aug 22	Aug 30	Sep 3	Sep 6	Sep 9	Sep 12	Sep 15	Sep 18	Sep 22
24°F	Sep 5	Sep 10	Sep 14	Sep 17	Sep 20	Sep 23	Sep 25	Sep 29	Oct 3
20°F	Sep 16	Sep 22	Sep 26	Sep 28	Oct 1	Oct 4	Oct 6	Oct 11	Oct 16
16°F	Sep 28	Oct 2	Oct 7	Oct 10	Oct 13	Oct 16	Oct 19	Oct 22	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	45	38	33	29	26	24	21	18	14
32°F	73	67	61	56	51	46	41	37	32
28°F	101	94	89	85	80	75	71	66	57
24°F	130	122	116	112	107	104	99	94	87
20°F	160	153	148	143	138	133	127	121	111
16°F	192	184	179	173	169	165	160	153	142

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: 9,792
Cooling degree days, base 65°F: 17
Growing degree days, base 40°F: 2,240
Growing degree days, base 45°F: 1,453
Growing degree days, base 50°F: 830
Growing degree days, base 55°F: 374
Growing degree days, base 60°F: 108

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	1,440	0	0
February	1,235	0	0
March	1,087	0	0
April	860	0	4
May	623	0	38
June	383	1	120
July	173	10	304
August	209	6	269
September	438	0	87
October	792	0	8
November	1,119	0	0
December	1,434	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 17.9 km from Summit 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 USC00421590 (Coalville 13 E). Public domain.