Southeast Fairbanks Census Area Frost Dates and Growing Season

NOAA 1991-2020 normals for Tok, 47.6 km from Southeast Fairbanks Census Area, elevation 1625 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Tok. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

NOAA does not state freeze dates for this station.

Median at 28°F: last May 28, first August 28

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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	–	–	–	–	–	–	–	–	–
32°F	–	–	–	–	–	–	–	–	–
28°F	Jun 10	Jun 5	Jun 1	May 30	May 28	May 25	May 22	May 18	May 12
24°F	May 31	May 26	May 21	May 17	May 14	May 11	May 8	May 5	May 2
20°F	May 18	May 12	May 8	May 5	May 2	Apr 30	Apr 28	Apr 24	Apr 18
16°F	May 5	May 1	Apr 29	Apr 26	Apr 23	Apr 21	Apr 18	Apr 14	Apr 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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	–	–	–	–	–	–	–	–	–
32°F	–	–	–	–	–	–	–	–	–
28°F	Aug 12	Aug 18	Aug 22	Aug 25	Aug 28	Aug 31	Sep 3	Sep 7	Sep 13
24°F	Aug 27	Sep 1	Sep 4	Sep 8	Sep 12	Sep 17	Sep 20	Sep 23	Sep 29
20°F	Sep 7	Sep 14	Sep 18	Sep 22	Sep 26	Sep 30	Oct 1	Oct 4	Oct 8
16°F	Sep 17	Sep 23	Sep 27	Oct 1	Oct 3	Oct 5	Oct 7	Oct 10	Oct 14

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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	59	49	44	40	36	33	30	25	21
32°F	86	78	72	68	64	59	54	48	40
28°F	114	107	101	96	92	87	83	77	70
24°F	142	135	129	125	120	116	110	104	97
20°F	163	156	152	148	145	141	137	131	122
16°F	178	173	169	165	162	157	153	149	143

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: 14,685
Cooling degree days, base 65°F: 22
Growing degree days, base 40°F: 1,857
Growing degree days, base 45°F: 1,200
Growing degree days, base 50°F: 672
Growing degree days, base 55°F: 300
Growing degree days, base 60°F: 93

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	2,382	0	0
February	1,889	0	0
March	1,717	0	0
April	1,016	0	1
May	592	0	34
June	263	8	207
July	192	9	284
August	361	4	135
September	687	0	12
October	1,311	0	0
November	1,948	0	0
December	2,327	0	0

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 47.6 km from Southeast Fairbanks Census Area. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00509313 (Tok). Public domain.