Fossil climate

Fossil Frost Dates and Growing Season

NOAA 1991-2020 normals for Fossil, 0.1 km from Fossil, elevation 2650 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Fossil. 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 June 3 and the first fall freeze around September 14, a growing season of about 98 days.

Median at 32°F
last June 3, first September 14
Median at 28°F
last May 10, first October 2

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°F–––––––––
32°FJul 3Jun 24Jun 17Jun 10Jun 3May 30May 26May 20May 13
28°FJun 1May 23May 17May 13May 10May 6May 2Apr 29Apr 24
24°FMay 10May 4Apr 30Apr 27Apr 24Apr 20Apr 16Apr 11Mar 31
20°FApr 23Apr 16Apr 11Apr 6Apr 1Mar 28Mar 21Mar 13Mar 2
16°FApr 4Mar 26Mar 15Mar 8Mar 2Feb 26Feb 19Feb 12Jan 24

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°F–––––––––
32°FAug 25Sep 1Sep 5Sep 9Sep 14Sep 18Sep 23Sep 29Oct 3
28°FSep 10Sep 21Sep 25Sep 30Oct 2Oct 5Oct 9Oct 14Oct 23
24°FSep 29Oct 3Oct 8Oct 13Oct 17Oct 23Oct 27Nov 1Nov 8
20°FOct 9Oct 17Oct 23Oct 28Nov 1Nov 7Nov 13Nov 21Dec 1
16°FOct 19Oct 30Nov 6Nov 13Nov 21Nov 27Dec 3Dec 10Dec 19

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°F837467615448423629
32°F1291201121059890837564
28°F168159153147142136129122113
24°F205194187183177172166158148
20°F256242233224215208200191180
16°F304289279269262252243233218

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
6,565
Cooling degree days, base 65°F
174
Growing degree days, base 40°F
3,623
Growing degree days, base 45°F
2,484
Growing degree days, base 50°F
1,603
Growing degree days, base 55°F
935
Growing degree days, base 60°F
460

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January96101
February81802
March77505
April612023
May4123117
June24215236
July8080465
August8366448
September24710232
October524067
November80205
December1,00900

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 0.1 km from Fossil. 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 USC00353038 (Fossil). Public domain.