Marion climate

Marion Frost Dates and Growing Season

NOAA 1991-2020 normals for Chambersburg 1 Ese, 9.9 km from Marion, elevation 640 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Chambersburg 1 Ese. 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 18 and the first fall freeze around October 25, a growing season of about 188 days.

Median at 36°F
last April 30, first October 14
Median at 32°F
last April 18, first October 25
Median at 28°F
last April 4, first November 6

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 17May 10May 7May 3Apr 30Apr 28Apr 25Apr 21Apr 16
32°FMay 5Apr 30Apr 25Apr 21Apr 18Apr 15Apr 11Apr 8Apr 3
28°FApr 21Apr 15Apr 11Apr 7Apr 4Apr 2Mar 30Mar 27Mar 21
24°FApr 6Apr 1Mar 30Mar 27Mar 24Mar 21Mar 17Mar 13Mar 7
20°FMar 28Mar 23Mar 19Mar 16Mar 12Mar 9Mar 5Mar 1Feb 25
16°FMar 18Mar 13Mar 9Mar 5Mar 2Feb 28Feb 23Feb 18Feb 10

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 1Oct 5Oct 8Oct 11Oct 14Oct 16Oct 19Oct 22Oct 28
32°FOct 10Oct 15Oct 19Oct 22Oct 25Oct 28Nov 1Nov 3Nov 8
28°FOct 23Oct 28Nov 1Nov 3Nov 6Nov 8Nov 12Nov 16Nov 21
24°FNov 2Nov 7Nov 11Nov 14Nov 18Nov 22Nov 26Dec 1Dec 5
20°FNov 14Nov 20Nov 25Nov 29Dec 1Dec 5Dec 9Dec 15Dec 23
16°FNov 29Dec 3Dec 8Dec 13Dec 17Dec 22Dec 26Dec 30Jan 7

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°F185179174169165161157151143
32°F208203198193188183178173165
28°F234227221217213208204198191
24°F262254248244238234230224217
20°F287279273268263259254248242
16°F312304298293288284278271263

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
5,302
Cooling degree days, base 65°F
926
Growing degree days, base 40°F
5,695
Growing degree days, base 45°F
4,450
Growing degree days, base 50°F
3,351
Growing degree days, base 55°F
2,396
Growing degree days, base 60°F
1,588

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,08003
February90304
March740133
April3879146
May15058378
June21192621
July1305769
August5251711
September7897471
October34412178
November645033
December94906

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 9.9 km from Marion. 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 USC00361354 (Chambersburg 1 Ese). Public domain.