Del Norte County climate

Del Norte County Frost Dates and Growing Season

NOAA 1991-2020 normals for Klamath, 20.9 km from Del Norte County, elevation 28 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Klamath. 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 March 16 and the first fall freeze around November 20, a growing season of about 252 days.

Median at 36°F
last April 21, first November 2
Median at 32°F
last March 16, first November 20
Median at 28°F
last February 4, first December 11

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.

Threshold10%20%30%40%50%60%70%80%90%
36°FJun 19Jun 8May 9Apr 28Apr 21Apr 15Apr 7Mar 31Mar 22
32°FApr 20Apr 8Mar 30Mar 23Mar 16Mar 7Feb 28Feb 21Feb 8
28°FMar 15Mar 2Feb 24Feb 15Feb 4Jan 15Jan 4Dec 26Dec 12
24°FFeb 24Feb 6Jan 12Jan 1Dec 27Dec 21Dec 14Dec 9Dec 2
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.

Threshold10%20%30%40%50%60%70%80%90%
36°FOct 11Oct 21Oct 27Oct 31Nov 2Nov 6Nov 10Nov 15Nov 23
32°FOct 30Nov 4Nov 9Nov 14Nov 20Nov 26Dec 1Dec 7Dec 18
28°FNov 13Nov 24Dec 1Dec 6Dec 11Dec 18Dec 26Jan 5Feb 2
24°FNov 28Dec 3Dec 8Dec 13Dec 19Dec 26Dec 31Jan 19Feb 13
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.

Threshold10%20%30%40%50%60%70%80%90%
36°F231219210203194184170154134
32°F295278268259252243233221200
28°F365355338329319308297284265
24°F365365365365365365360343319
20°F365365365365365365365365365
16°F365365365365365365365365365

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
88% of years
24°F or colder
39% of years
20°F or colder
7% of years
16°F or colder
1% 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
4,602
Cooling degree days, base 65°F
7
Growing degree days, base 40°F
4,549
Growing degree days, base 45°F
2,865
Growing degree days, base 50°F
1,481
Growing degree days, base 55°F
548
Growing degree days, base 60°F
98

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January557020
February491028
March513037
April429069
May3460136
June2900169
July1742296
August1991269
September2072248
October3391145
November473050
December586013

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 20.9 km from Del Norte County. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00044577 (Klamath). Public domain.