Marion County climate

Marion County Frost Dates and Growing Season

NOAA 1991-2020 normals for Silver Creek Falls, 6 km from Marion County, elevation 1350 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Silver Creek Falls. 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 30 and the first fall freeze around October 22, a growing season of about 174 days.

Median at 36°F
last May 17, first October 3
Median at 32°F
last April 30, first October 22
Median at 28°F
last March 30, first November 13

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 4May 30May 25May 21May 17May 14May 11May 7May 2
32°FMay 15May 9May 5May 3Apr 30Apr 27Apr 24Apr 19Apr 10
28°FApr 28Apr 20Apr 12Apr 5Mar 30Mar 24Mar 17Mar 9Feb 28
24°FMar 17Mar 5Feb 28Feb 22Feb 16Feb 5Jan 27Jan 8Dec 24
20°FFeb 25Feb 19Feb 9Jan 29Jan 11Jan 1Dec 22Dec 11Dec 2
16°FFeb 20Feb 4Jan 12Dec 30Dec 22Dec 17Dec 9Dec 4Nov 30

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 15Sep 22Sep 27Sep 30Oct 3Oct 6Oct 9Oct 14Oct 21
32°FOct 2Oct 7Oct 13Oct 18Oct 22Oct 27Oct 31Nov 5Nov 12
28°FOct 21Oct 28Nov 2Nov 8Nov 13Nov 18Nov 27Dec 3Dec 13
24°FNov 10Nov 17Nov 26Dec 2Dec 8Dec 15Dec 24Jan 3Jan 27
20°FNov 19Nov 29Dec 4Dec 11Dec 20Dec 29Jan 8Feb 1Feb 16
16°FNov 27Dec 1Dec 6Dec 12Dec 19Dec 24Jan 1Jan 26Feb 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°F160152147142136131126120111
32°F203193186179174169165157149
28°F274255245236228220210202190
24°F352337322312304294284272252
20°F365365365363353340331318309
16°F365365365365365365365350334

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
95% of years
20°F or colder
63% of years
16°F or colder
27% 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
5,992
Cooling degree days, base 65°F
99
Growing degree days, base 40°F
3,635
Growing degree days, base 45°F
2,408
Growing degree days, base 50°F
1,481
Growing degree days, base 55°F
796
Growing degree days, base 60°F
338

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January84600
February72401
March71604
April576025
May3921121
June2589209
July9843411
August10038403
September2208243
October491058
November70505
December86600

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 6 km from Marion County. 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 USC00357809 (Silver Creek Falls). Public domain.