Ione Frost Dates and Growing Season

NOAA 1991-2020 normals for Camp Pardee, 14 km from Ione, elevation 658 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Camp Pardee. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around January 22 and the first fall freeze around December 17, a growing season of about 332 days.

Median at 36°F: last March 10, first December 3
Median at 32°F: last January 22, first December 17
Median at 28°F: last December 31, first December 27

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	Apr 11	Apr 2	Mar 26	Mar 17	Mar 10	Mar 3	Feb 25	Feb 15	Feb 2
32°F	Mar 1	Feb 20	Feb 8	Jan 30	Jan 22	Jan 14	Jan 6	Dec 31	Dec 23
28°F	Jan 29	Jan 18	Jan 8	Jan 4	Dec 31	Dec 29	Dec 25	Dec 20	Dec 14
24°F	–	–	–	–	–	–	–	–	–
20°F	–	–	–	–	–	–	–	–	–
16°F	–	–	–	–	–	–	–	–	–

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	Nov 15	Nov 21	Nov 26	Nov 30	Dec 3	Dec 6	Dec 10	Dec 15	Dec 23
32°F	Dec 1	Dec 5	Dec 9	Dec 13	Dec 17	Dec 21	Dec 28	Jan 3	Jan 17
28°F	Dec 9	Dec 15	Dec 19	Dec 23	Dec 27	Dec 31	Jan 4	Jan 11	Jan 25
24°F	–	–	–	–	–	–	–	–	–
20°F	–	–	–	–	–	–	–	–	–
16°F	–	–	–	–	–	–	–	–	–

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	308	291	281	274	266	259	251	242	232
32°F	364	353	345	339	332	325	313	304	291
28°F	365	365	365	365	365	365	362	353	342
24°F	365	365	365	365	365	365	365	365	365
20°F	365	365	365	365	365	365	365	365	365
16°F	365	365	365	365	365	365	365	365	365

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: 88% of years
28°F or colder: 33% of years
24°F or colder: 3% of years
20°F or colder: 0% of years
16°F or colder: 0% 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: 2,495
Cooling degree days, base 65°F: 1,624
Growing degree days, base 40°F: 8,266
Growing degree days, base 45°F: 6,503
Growing degree days, base 50°F: 4,910
Growing degree days, base 55°F: 3,575
Growing degree days, base 60°F: 2,495

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	539	0	32
February	392	0	69
March	324	2	165
April	213	20	262
May	85	103	484
June	10	262	702
July	0	429	894
August	1	413	877
September	7	290	734
October	75	102	492
November	307	4	169
December	542	0	31

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 km from Ione. 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 USC00041428 (Camp Pardee). Public domain.