Bison climate

Bison Frost Dates and Growing Season

NOAA 1991-2020 normals for Bison, 1 km from Bison, elevation 2780 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Bison. 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 10 and the first fall freeze around October 1, a growing season of about 144 days.

Median at 36°F
last May 19, first September 24
Median at 32°F
last May 10, first October 1
Median at 28°F
last May 1, first October 9

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 1May 28May 25May 22May 19May 17May 15May 12May 8
32°FMay 24May 18May 14May 12May 10May 7May 5May 2Apr 30
28°FMay 13May 9May 5May 3May 1Apr 28Apr 25Apr 21Apr 16
24°FMay 3Apr 30Apr 26Apr 23Apr 19Apr 17Apr 14Apr 11Apr 7
20°FApr 26Apr 20Apr 16Apr 14Apr 11Apr 8Apr 6Apr 3Mar 28
16°FApr 16Apr 12Apr 8Apr 5Apr 3Mar 31Mar 27Mar 22Mar 15

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 9Sep 14Sep 18Sep 21Sep 24Sep 26Sep 29Oct 1Oct 5
32°FSep 16Sep 22Sep 26Sep 29Oct 1Oct 3Oct 7Oct 11Oct 15
28°FSep 25Sep 30Oct 3Oct 7Oct 9Oct 13Oct 16Oct 19Oct 24
24°FOct 2Oct 7Oct 12Oct 15Oct 18Oct 21Oct 24Oct 27Nov 1
20°FOct 11Oct 16Oct 20Oct 24Oct 27Oct 30Nov 2Nov 6Nov 12
16°FOct 19Oct 25Oct 30Nov 1Nov 4Nov 8Nov 12Nov 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°F142137133129125121117113108
32°F161155151147144140136131124
28°F181174168164161157153147141
24°F199193188184180176171166160
20°F220212207203198193188183176
16°F240232226221216211207201193

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
7,612
Cooling degree days, base 65°F
632
Growing degree days, base 40°F
4,507
Growing degree days, base 45°F
3,468
Growing degree days, base 50°F
2,564
Growing degree days, base 55°F
1,789
Growing degree days, base 60°F
1,139

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,40600
February1,18701
March978011
April618150
May31216216
June8085456
July14243694
August22217660
September15866372
October556495
November962010
December1,32000

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 1 km from Bison. 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 USC00390701 (Bison). Public domain.