Denali Borough climate

Denali Borough Frost Dates and Growing Season

NOAA 1991-2020 normals for Denali 27 N, 50.4 km from Denali Borough, elevation 2225 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Denali 27 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 May 25 and the first fall freeze around September 8, a growing season of about 105 days.

Median at 36°F
last June 4, first August 27
Median at 32°F
last May 25, first September 8
Median at 28°F
last May 13, first September 19

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 16Jun 12Jun 9Jun 6Jun 4Jun 2May 31May 29May 26
32°FJun 3May 31May 29May 27May 25May 22May 20May 17May 13
28°FMay 24May 20May 17May 15May 13May 11May 9May 6May 3
24°FMay 13May 9May 7May 5May 3May 1Apr 29Apr 26Apr 22
20°FMay 4May 1Apr 29Apr 26Apr 24Apr 21Apr 19Apr 15Apr 12
16°FApr 27Apr 23Apr 21Apr 18Apr 15Apr 13Apr 11Apr 8Apr 5

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°FAug 14Aug 18Aug 22Aug 25Aug 27Aug 30Sep 2Sep 5Sep 9
32°FAug 26Aug 31Sep 3Sep 5Sep 8Sep 11Sep 13Sep 16Sep 20
28°FSep 5Sep 10Sep 14Sep 16Sep 19Sep 21Sep 23Sep 26Sep 29
24°FSep 15Sep 20Sep 23Sep 26Sep 27Sep 29Oct 1Oct 5Oct 9
20°FSep 24Sep 28Oct 1Oct 3Oct 6Oct 8Oct 11Oct 14Oct 17
16°FOct 1Oct 6Oct 8Oct 11Oct 13Oct 15Oct 18Oct 20Oct 23

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°F989389868279747062
32°F122117113109105102999589
28°F143138134130126123120116110
24°F162157153150147144140136131
20°F182176172168165162158154148
16°F196190186182179176173169163

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
13,188
Cooling degree days, base 65°F
5
Growing degree days, base 40°F
1,489
Growing degree days, base 45°F
860
Growing degree days, base 50°F
395
Growing degree days, base 55°F
123
Growing degree days, base 60°F
24

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,87500
February1,41900
March1,61300
April1,07600
May67707
June3571122
July2983179
August423082
September70605
October1,24500
November1,62600
December1,87200

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 50.4 km from Denali Borough. 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 USW00096408 (Denali 27 N). Public domain.