Salmon climate

Salmon Frost Dates and Growing Season

NOAA 1991-2020 normals for Salmon-Ksra, 0.9 km from Salmon, elevation 3953 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Salmon-Ksra. 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 May 17 and the first fall freeze around September 24, a growing season of about 127 days.

Median at 36°F
last June 7, first September 13
Median at 32°F
last May 17, first September 24
Median at 28°F
last May 2, first October 5

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 23Jun 18Jun 14Jun 11Jun 7Jun 4Jun 1May 27May 20
32°FJun 9May 31May 25May 21May 17May 14May 11May 7May 3
28°FMay 19May 11May 7May 5May 2Apr 30Apr 28Apr 24Apr 19
24°FMay 1Apr 27Apr 24Apr 20Apr 17Apr 13Apr 10Apr 5Mar 31
20°FApr 18Apr 11Apr 6Apr 2Mar 30Mar 25Mar 20Mar 15Mar 9
16°FMar 29Mar 20Mar 15Mar 12Mar 9Mar 7Mar 4Mar 1Feb 23

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°FAug 31Sep 4Sep 7Sep 10Sep 13Sep 15Sep 18Sep 20Sep 24
32°FSep 9Sep 15Sep 18Sep 22Sep 24Sep 26Sep 29Oct 2Oct 5
28°FSep 21Sep 26Sep 30Oct 2Oct 5Oct 7Oct 10Oct 14Oct 18
24°FOct 3Oct 7Oct 12Oct 15Oct 18Oct 20Oct 24Oct 28Nov 1
20°FOct 13Oct 20Oct 24Oct 27Oct 30Nov 1Nov 4Nov 7Nov 13
16°FOct 25Oct 30Nov 1Nov 5Nov 8Nov 11Nov 16Nov 20Nov 25

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°F116110104999592878376
32°F145139135131127122116108100
28°F174167162157153149145141132
24°F205198192186182178173168160
20°F236228223219214209203197190
16°F263257251246241237232226218

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
7,765
Cooling degree days, base 65°F
293
Growing degree days, base 40°F
3,749
Growing degree days, base 45°F
2,754
Growing degree days, base 50°F
1,911
Growing degree days, base 55°F
1,219
Growing degree days, base 60°F
679

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,40700
February1,09100
March85302
April596029
May3443165
June15635334
July26148587
August4397519
September23610239
October633035
November1,01401
December1,36700

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 0.9 km from Salmon. 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 USC00108080 (Salmon-Ksra). Public domain.