Earth climate

Earth Frost Dates and Growing Season

NOAA 1991-2020 normals for Olton, 26 km from Earth, elevation 3640 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Olton. 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 April 6 and the first fall freeze around November 1, a growing season of about 206 days.

Median at 36°F
last April 19, first October 22
Median at 32°F
last April 6, first November 1
Median at 28°F
last March 27, first November 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°FMay 2Apr 28Apr 24Apr 21Apr 19Apr 16Apr 12Apr 8Apr 5
32°FApr 23Apr 18Apr 13Apr 9Apr 6Apr 4Apr 1Mar 29Mar 22
28°FApr 11Apr 5Apr 2Mar 31Mar 27Mar 22Mar 16Mar 11Mar 5
24°FMar 31Mar 24Mar 19Mar 14Mar 11Mar 7Mar 4Feb 28Feb 23
20°FMar 16Mar 10Mar 6Mar 3Feb 28Feb 24Feb 20Feb 16Feb 7
16°FMar 6Mar 1Feb 24Feb 19Feb 14Feb 9Feb 5Jan 29Jan 16

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°FOct 8Oct 13Oct 17Oct 19Oct 22Oct 24Oct 27Oct 30Nov 3
32°FOct 17Oct 22Oct 26Oct 28Nov 1Nov 3Nov 5Nov 8Nov 13
28°FOct 27Nov 1Nov 4Nov 7Nov 9Nov 13Nov 16Nov 20Nov 24
24°FNov 3Nov 9Nov 13Nov 16Nov 20Nov 23Nov 27Dec 1Dec 5
20°FNov 14Nov 20Nov 24Nov 28Dec 1Dec 3Dec 7Dec 12Dec 19
16°FNov 24Nov 30Dec 5Dec 9Dec 13Dec 19Dec 24Dec 30Jan 10

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°F204198193189185181176171166
32°F227219214210206201197191183
28°F252244239234229224218212206
24°F275269263258253249243237230
20°F298291285281276271266259251
16°F337324316308303297290283272

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
99% 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
3,772
Cooling degree days, base 65°F
1,469
Growing degree days, base 40°F
7,231
Growing degree days, base 45°F
5,749
Growing degree days, base 50°F
4,429
Growing degree days, base 55°F
3,282
Growing degree days, base 60°F
2,298

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January811011
February634029
March4713114
April23521265
May72136531
June2323771
July0411876
August1367831
September33179597
October21130310
November514182
December787013

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 26 km from Earth. 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 USC00416644 (Olton). Public domain.