Teton climate

Teton Frost Dates and Growing Season

NOAA 1991-2020 normals for Saint Anthony, 7.2 km from Teton, elevation 4910 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Saint Anthony. 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 22, a growing season of about 126 days.

Median at 36°F
last June 8, first September 10
Median at 32°F
last May 17, first September 22
Median at 28°F
last May 4, first October 4

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 30Jun 21Jun 16Jun 12Jun 8Jun 5Jun 2May 28May 21
32°FJun 10Jun 1May 25May 21May 17May 14May 11May 8May 4
28°FMay 17May 12May 9May 7May 4May 2Apr 30Apr 27Apr 21
24°FMay 7May 1Apr 29Apr 26Apr 22Apr 18Apr 15Apr 10Apr 5
20°FApr 25Apr 19Apr 15Apr 11Apr 7Apr 4Apr 1Mar 28Mar 20
16°FApr 10Apr 4Apr 1Mar 29Mar 26Mar 21Mar 16Mar 12Mar 7

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 26Sep 1Sep 4Sep 7Sep 10Sep 13Sep 17Sep 20Sep 25
32°FSep 5Sep 10Sep 15Sep 19Sep 22Sep 25Sep 28Oct 2Oct 7
28°FSep 17Sep 24Sep 28Oct 1Oct 4Oct 6Oct 10Oct 14Oct 20
24°FSep 28Oct 2Oct 6Oct 11Oct 15Oct 18Oct 21Oct 26Nov 1
20°FOct 6Oct 14Oct 18Oct 23Oct 26Oct 30Nov 2Nov 6Nov 12
16°FOct 19Oct 25Oct 29Nov 1Nov 5Nov 8Nov 12Nov 17Nov 22

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°F118111104999388837767
32°F14814113713112612111510999
28°F172165160155152148143139131
24°F196189184179175170165159152
20°F225216209205200195190184175
16°F249240234229225219214207199

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
8,167
Cooling degree days, base 65°F
215
Growing degree days, base 40°F
3,484
Growing degree days, base 45°F
2,525
Growing degree days, base 50°F
1,721
Growing degree days, base 55°F
1,062
Growing degree days, base 60°F
558

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,40300
February1,17000
March98401
April660021
May4061127
June19221288
July45104524
August5678488
September25611231
October631039
November1,00401
December1,36100

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 7.2 km from Teton. 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 USC00108022 (Saint Anthony). Public domain.