Granite County Frost Dates and Growing Season

NOAA 1991-2020 normals for Phillipsburg RS, 14.5 km from Granite County, elevation 5270 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Phillipsburg RS. 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 May 29, first September 12

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 18	Jun 10	Jun 4	Jun 1	May 29	May 26	May 23	May 19	May 13
24°F	May 28	May 23	May 19	May 15	May 13	May 10	May 7	May 4	Apr 30
20°F	May 14	May 9	May 6	May 3	May 1	Apr 29	Apr 24	Apr 19	Apr 13
16°F	May 4	Apr 29	Apr 24	Apr 20	Apr 16	Apr 12	Apr 8	Apr 3	Mar 27

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 2	Sep 5	Sep 9	Sep 12	Sep 16	Sep 19	Sep 22	Sep 27
24°F	Sep 9	Sep 16	Sep 20	Sep 23	Sep 26	Sep 30	Oct 2	Oct 5	Oct 11
20°F	Sep 22	Sep 28	Oct 2	Oct 5	Oct 8	Oct 12	Oct 16	Oct 21	Oct 24
16°F	Oct 2	Oct 8	Oct 13	Oct 17	Oct 22	Oct 25	Oct 28	Nov 1	Nov 5

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	53	46	39	35	31	27	24	21	18
32°F	90	81	75	69	65	60	54	48	39
28°F	127	120	115	110	105	101	97	90	80
24°F	156	148	143	139	134	130	126	120	112
20°F	184	175	168	164	160	156	151	147	139
16°F	215	206	199	192	187	182	176	171	161

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: 8,421
Cooling degree days, base 65°F: 60
Growing degree days, base 40°F: 2,784
Growing degree days, base 45°F: 1,880
Growing degree days, base 50°F: 1,159
Growing degree days, base 55°F: 614
Growing degree days, base 60°F: 248

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	1,226	0	0
February	1,088	0	0
March	966	0	1
April	753	0	7
May	524	0	65
June	298	4	178
July	121	31	376
August	140	22	351
September	352	2	150
October	696	0	28
November	996	0	2
December	1,262	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 14.5 km from Granite 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 USC00246472 (Phillipsburg RS). Public domain.