Deltana climate

Deltana Frost Dates and Growing Season

NOAA 1991-2020 normals for Delta Junction 20 Se, 11.7 km from Deltana, elevation 1125 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Delta Junction 20 Se. 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 June 5 and the first fall freeze around August 21, a growing season of about 75 days.

Median at 32°F
last June 5, first August 21
Median at 28°F
last May 25, first September 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°F–––––––––
32°FJun 30Jun 16Jun 11Jun 8Jun 5Jun 2May 31May 29May 25
28°FJun 5Jun 1May 30May 27May 25May 22May 19May 17May 12
24°FMay 28May 22May 18May 15May 12May 9May 6May 4Apr 30
20°FMay 15May 9May 6May 3May 1Apr 29Apr 25Apr 22Apr 16
16°FMay 4Apr 30Apr 27Apr 24Apr 21Apr 19Apr 15Apr 13Apr 9

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°F–––––––––
32°FAug 8Aug 12Aug 15Aug 18Aug 21Aug 23Aug 26Aug 28Sep 1
28°FAug 19Aug 24Aug 28Aug 30Sep 1Sep 3Sep 5Sep 8Sep 14
24°FSep 1Sep 5Sep 8Sep 11Sep 14Sep 17Sep 20Sep 23Sep 26
20°FSep 12Sep 16Sep 20Sep 22Sep 25Sep 27Sep 30Oct 3Oct 8
16°FSep 21Sep 25Sep 28Oct 1Oct 3Oct 5Oct 9Oct 12Oct 16

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°F686156524844393327
32°F928782797571676153
28°F1151101061029995928881
24°F143136131127123119116111104
20°F166159154150146142137133126
16°F181175172168164160155151144

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
13,718
Cooling degree days, base 65°F
13
Growing degree days, base 40°F
1,844
Growing degree days, base 45°F
1,179
Growing degree days, base 50°F
657
Growing degree days, base 55°F
291
Growing degree days, base 60°F
87

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January2,13400
February1,72200
March1,68800
April1,00501
May588035
June2647208
July2006275
August3681129
September69008
October1,25601
November1,76800
December2,03700

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 11.7 km from Deltana. 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 USC00502352 (Delta Junction 20 Se). Public domain.