Marion climate

Marion Frost Dates and Growing Season

NOAA 1991-2020 normals for Marion 2 N, 3.1 km from Marion, elevation 965 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Marion 2 N. 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 25 and the first fall freeze around October 20, a growing season of about 178 days.

Median at 36°F
last May 5, first October 8
Median at 32°F
last April 25, first October 20
Median at 28°F
last April 14, first November 1

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 21May 15May 11May 8May 5May 2Apr 29Apr 25Apr 21
32°FMay 11May 6May 2Apr 28Apr 25Apr 22Apr 19Apr 16Apr 11
28°FMay 3Apr 24Apr 20Apr 17Apr 14Apr 10Apr 6Apr 3Mar 30
24°FApr 19Apr 12Apr 8Apr 4Apr 2Mar 31Mar 28Mar 24Mar 18
20°FApr 7Apr 2Mar 30Mar 26Mar 23Mar 20Mar 17Mar 12Mar 7
16°FMar 29Mar 24Mar 19Mar 16Mar 13Mar 10Mar 7Mar 1Feb 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°FSep 24Sep 30Oct 3Oct 6Oct 8Oct 11Oct 14Oct 17Oct 21
32°FOct 5Oct 11Oct 14Oct 17Oct 20Oct 23Oct 26Oct 29Nov 2
28°FOct 18Oct 22Oct 26Oct 29Nov 1Nov 2Nov 5Nov 9Nov 14
24°FOct 29Nov 1Nov 4Nov 8Nov 11Nov 14Nov 18Nov 23Nov 28
20°FNov 6Nov 11Nov 16Nov 19Nov 23Nov 27Dec 1Dec 4Dec 11
16°FNov 15Nov 21Nov 27Dec 1Dec 4Dec 8Dec 14Dec 19Dec 25

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°F174168164160157151147142136
32°F198191186182178174169163154
28°F221213209205200195191185177
24°F244238231226223218214209200
20°F269261255249245241235229222
16°F292283277271266261255249242

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
6,015
Cooling degree days, base 65°F
799
Growing degree days, base 40°F
5,323
Growing degree days, base 45°F
4,147
Growing degree days, base 50°F
3,104
Growing degree days, base 55°F
2,201
Growing degree days, base 60°F
1,429

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,21002
February1,01903
March850128
April4706114
May19257341
June31180598
July4256718
August11205659
September9682439
October38011164
November710133
December1,04205

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 3.1 km from Marion. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00334942 (Marion 2 N). Public domain.