Klamath County Frost Dates and Growing Season

NOAA 1991-2020 normals for Chiloquin 12 Nw (fort Klamath), 28.3 km from Klamath County, elevation 4180 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Chiloquin 12 Nw (fort Klamath). 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 10, first September 13

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 28	Jun 23	Jun 18	Jun 14	Jun 10	Jun 4	May 31	May 26	May 18
24°F	Jun 12	Jun 2	May 27	May 21	May 17	May 11	May 5	Apr 30	Apr 24
20°F	May 12	May 6	May 1	Apr 26	Apr 20	Apr 13	Apr 6	Mar 31	Mar 22
16°F	Apr 20	Apr 9	Apr 3	Mar 29	Mar 23	Mar 17	Mar 10	Mar 4	Feb 25

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 27	Sep 2	Sep 5	Sep 9	Sep 13	Sep 16	Sep 20	Sep 24	Sep 30
24°F	Sep 12	Sep 19	Sep 24	Sep 28	Oct 1	Oct 3	Oct 7	Oct 12	Oct 18
20°F	Sep 30	Oct 4	Oct 9	Oct 13	Oct 18	Oct 23	Oct 26	Nov 1	Nov 7
16°F	Oct 13	Oct 21	Oct 26	Nov 1	Nov 3	Nov 8	Nov 13	Nov 20	Nov 29

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	47	41	36	32	28	26	22	19	15
32°F	86	76	70	64	59	53	48	41	33
28°F	121	113	106	99	93	86	80	73	63
24°F	166	155	148	142	135	129	123	116	104
20°F	214	202	193	186	179	171	163	156	146
16°F	260	248	239	232	224	218	210	201	187

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: 7,365
Cooling degree days, base 65°F: 98
Growing degree days, base 40°F: 3,119
Growing degree days, base 45°F: 2,132
Growing degree days, base 50°F: 1,357
Growing degree days, base 55°F: 757
Growing degree days, base 60°F: 331

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	1,119	0	0
February	900	0	0
March	849	0	1
April	671	0	14
May	472	1	89
June	273	9	208
July	95	48	420
August	114	35	388
September	280	6	202
October	598	0	35
November	875	0	1
December	1,119	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 28.3 km from Klamath 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 USC00351574 (Chiloquin 12 Nw (fort Klamath)). Public domain.