Seneca climate

Seneca Frost Dates and Growing Season

NOAA 1991-2020 normals for Franklin, 10.8 km from Seneca, elevation 1015 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Franklin. 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 May 2 and the first fall freeze around October 23, a growing season of about 171 days.

Median at 36°F
last May 13, first October 9
Median at 32°F
last May 2, first October 23
Median at 28°F
last April 21, first November 3

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 28May 24May 21May 18May 13May 10May 7May 3Apr 29
32°FMay 20May 15May 9May 6May 2Apr 30Apr 27Apr 23Apr 20
28°FMay 8May 2Apr 28Apr 24Apr 21Apr 19Apr 16Apr 12Apr 7
24°FApr 21Apr 16Apr 13Apr 10Apr 7Apr 5Apr 2Mar 31Mar 25
20°FApr 9Apr 5Apr 2Mar 31Mar 28Mar 24Mar 21Mar 16Mar 11
16°FMar 31Mar 27Mar 23Mar 19Mar 17Mar 14Mar 11Mar 7Mar 2

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 29Oct 1Oct 4Oct 7Oct 9Oct 12Oct 15Oct 18Oct 23
32°FOct 8Oct 14Oct 17Oct 20Oct 23Oct 25Oct 29Nov 1Nov 4
28°FOct 22Oct 27Oct 30Nov 1Nov 3Nov 6Nov 8Nov 11Nov 15
24°FNov 2Nov 6Nov 9Nov 11Nov 14Nov 17Nov 19Nov 23Nov 29
20°FNov 10Nov 15Nov 18Nov 22Nov 25Nov 28Dec 1Dec 7Dec 14
16°FNov 17Nov 25Nov 30Dec 3Dec 7Dec 11Dec 16Dec 22Dec 28

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°F170162158153149145141136130
32°F190184180175171167163158153
28°F214207202198195191186182175
24°F240231227223220216212208201
20°F263255250245241237232228221
16°F287280274268264259253248240

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
6,365
Cooling degree days, base 65°F
584
Growing degree days, base 40°F
4,810
Growing degree days, base 45°F
3,684
Growing degree days, base 50°F
2,697
Growing degree days, base 55°F
1,850
Growing degree days, base 60°F
1,140

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,20901
February1,05001
March915016
April529280
May23736287
June54117513
July10201656
August15162612
September12260392
October4376120
November740018
December1,04803

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 10.8 km from Seneca. 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 USC00363028 (Franklin). Public domain.