Delphi climate

Delphi Frost Dates and Growing Season

NOAA 1991-2020 normals for Delphi 2 N, 3.1 km from Delphi, elevation 556 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Delphi 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 22 and the first fall freeze around October 17, a growing season of about 179 days.

Median at 36°F
last May 2, first October 6
Median at 32°F
last April 22, first October 17
Median at 28°F
last April 8, first October 30

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

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 23Sep 28Oct 1Oct 3Oct 6Oct 8Oct 11Oct 15Oct 21
32°FOct 3Oct 8Oct 12Oct 14Oct 17Oct 21Oct 24Oct 28Nov 1
28°FOct 16Oct 20Oct 24Oct 27Oct 30Nov 1Nov 4Nov 7Nov 13
24°FOct 29Nov 1Nov 4Nov 7Nov 10Nov 14Nov 18Nov 22Nov 28
20°FNov 6Nov 10Nov 14Nov 19Nov 22Nov 26Dec 1Dec 4Dec 10
16°FNov 14Nov 19Nov 24Nov 28Dec 1Dec 5Dec 10Dec 15Dec 22

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°F175168164159156152147142135
32°F199193188183179176171165157
28°F224216211207203199195189181
24°F252243237232228223218213205
20°F276267259254249244239233225
16°F295286279274268263258252244

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
5,570
Cooling degree days, base 65°F
928
Growing degree days, base 40°F
5,717
Growing degree days, base 45°F
4,494
Growing degree days, base 50°F
3,403
Growing degree days, base 55°F
2,440
Growing degree days, base 60°F
1,610

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,18402
February96404
March744142
April39014157
May14077406
June21205634
July2278741
August7233691
September76103478
October33618201
November680141
December1,02706

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 Delphi. 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 USC00122149 (Delphi 2 N). Public domain.