Jackson County Frost Dates and Growing Season

NOAA 1991-2020 normals for Walden, 10.2 km from Jackson County, elevation 8056 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Walden. 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.

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	–	–	–	–	–	–	–	–	–
24°F	Jun 9	Jun 4	Jun 1	May 29	May 25	May 23	May 20	May 16	May 12
20°F	May 27	May 21	May 17	May 14	May 12	May 9	May 7	May 4	May 1
16°F	May 16	May 12	May 8	May 6	May 4	May 1	Apr 29	Apr 25	Apr 20

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	–	–	–	–	–	–	–	–	–
24°F	Aug 27	Sep 1	Sep 4	Sep 7	Sep 9	Sep 12	Sep 14	Sep 18	Sep 22
20°F	Sep 7	Sep 11	Sep 14	Sep 18	Sep 20	Sep 23	Sep 26	Sep 30	Oct 3
16°F	Sep 15	Sep 21	Sep 24	Sep 27	Oct 1	Oct 3	Oct 6	Oct 9	Oct 15

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	20	16	14	13	11	10	9	8	7
32°F	50	43	38	35	31	27	24	21	16
28°F	92	84	79	74	69	64	59	53	44
24°F	123	117	111	108	104	101	96	92	85
20°F	147	141	137	133	129	125	122	117	110
16°F	167	161	157	152	148	144	140	135	128

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: 10,822
Cooling degree days, base 65°F: 1
Growing degree days, base 40°F: 1,831
Growing degree days, base 45°F: 1,106
Growing degree days, base 50°F: 546
Growing degree days, base 55°F: 181
Growing degree days, base 60°F: 28

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	1,572	0	0
February	1,344	0	0
March	1,214	0	0
April	939	0	0
May	687	0	12
June	401	0	93
July	241	1	227
August	304	0	171
September	513	0	42
October	874	0	1
November	1,199	0	0
December	1,536	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 10.2 km from Jackson 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 USC00058756 (Walden). Public domain.