Three Forks climate

Three Forks Frost Dates and Growing Season

NOAA 1991-2020 normals for Trident, 8.5 km from Three Forks, elevation 4036 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Trident. 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 9 and the first fall freeze around September 27, a growing season of about 139 days.

Median at 36°F
last May 24, first September 15
Median at 32°F
last May 9, first September 27
Median at 28°F
last April 29, first October 6

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 10Jun 3May 31May 28May 24May 21May 17May 14May 10
32°FMay 24May 18May 14May 11May 9May 6May 4May 2Apr 29
28°FMay 10May 6May 3May 1Apr 29Apr 26Apr 23Apr 19Apr 12
24°FApr 30Apr 27Apr 22Apr 18Apr 15Apr 12Apr 8Apr 3Mar 29
20°FApr 17Apr 13Apr 8Apr 4Apr 1Mar 29Mar 24Mar 17Mar 10
16°FApr 8Apr 2Mar 28Mar 23Mar 18Mar 14Mar 10Mar 4Feb 28

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 1Sep 6Sep 10Sep 12Sep 15Sep 19Sep 22Sep 25Sep 30
32°FSep 12Sep 18Sep 22Sep 24Sep 27Sep 29Oct 2Oct 5Oct 9
28°FSep 24Sep 28Oct 1Oct 4Oct 6Oct 10Oct 13Oct 17Oct 22
24°FOct 1Oct 4Oct 9Oct 13Oct 17Oct 20Oct 24Oct 28Nov 1
20°FOct 9Oct 16Oct 20Oct 25Oct 29Nov 1Nov 2Nov 6Nov 11
16°FOct 18Oct 24Oct 30Nov 1Nov 5Nov 8Nov 11Nov 15Nov 20

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°F1311241191161121071029790
32°F156151147143139136131127120
28°F181174170165161157153149143
24°F207198193189184179175169161
20°F233224218214209203198192184
16°F254246240235229223218212203

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
7,434
Cooling degree days, base 65°F
334
Growing degree days, base 40°F
3,907
Growing degree days, base 45°F
2,864
Growing degree days, base 50°F
1,997
Growing degree days, base 55°F
1,286
Growing degree days, base 60°F
729

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,25700
February1,05301
March87305
April617029
May3573161
June14935339
July29159595
August45117539
September22019268
October596157
November97004
December1,26900

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 8.5 km from Three Forks. 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 USC00248363 (Trident). Public domain.