Dunsmuir climate

Dunsmuir Frost Dates and Growing Season

NOAA 1991-2020 normals for Dunsmuir Trtmt Pl, 2.9 km from Dunsmuir, elevation 2169 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Dunsmuir Trtmt Pl. 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 April 23 and the first fall freeze around October 27, a growing season of about 185 days.

Median at 36°F
last May 11, first October 9
Median at 32°F
last April 23, first October 27
Median at 28°F
last March 31, first November 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.

Threshold10%20%30%40%50%60%70%80%90%
36°FJun 3May 28May 20May 15May 11May 8May 5May 1Apr 27
32°FMay 12May 5May 1Apr 27Apr 23Apr 20Apr 17Apr 12Apr 5
28°FApr 21Apr 16Apr 10Apr 5Mar 31Mar 27Mar 21Mar 12Mar 1
24°FMar 28Mar 11Mar 3Feb 27Feb 20Feb 14Feb 4Jan 27Jan 11
20°FFeb 23Feb 11Feb 2Jan 25Jan 15Jan 8Jan 1Dec 23Dec 12
16°FJan 26Jan 17Jan 9Jan 3Dec 31Dec 25Dec 20Dec 15Dec 9

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°FSep 23Sep 28Oct 1Oct 5Oct 9Oct 13Oct 16Oct 20Oct 24
32°FOct 9Oct 16Oct 20Oct 24Oct 27Oct 30Nov 1Nov 5Nov 10
28°FOct 28Nov 2Nov 6Nov 9Nov 12Nov 16Nov 21Nov 26Dec 2
24°FNov 11Nov 18Nov 24Nov 30Dec 3Dec 7Dec 13Dec 20Jan 3
20°FNov 28Dec 4Dec 10Dec 15Dec 21Dec 29Jan 4Jan 16Jan 31
16°FDec 7Dec 12Dec 17Dec 20Dec 25Dec 31Jan 6Jan 15Jan 21

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°F172164158154149144139133123
32°F208200195189185180174168158
28°F259248240232225220214207197
24°F328313301294285276268258243
20°F365365360352345337331319305
16°F365365365365365365365363349

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
99% of years
20°F or colder
73% of years
16°F or colder
21% 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
4,621
Cooling degree days, base 65°F
588
Growing degree days, base 40°F
5,342
Growing degree days, base 45°F
3,960
Growing degree days, base 50°F
2,829
Growing degree days, base 55°F
1,905
Growing degree days, base 60°F
1,163

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January79801
February65504
March611026
April444086
May22522276
June7495473
July7222680
August9173629
September7470446
October3136184
November601022
December80901

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 2.9 km from Dunsmuir. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00042574 (Dunsmuir Trtmt Pl). Public domain.