Dubois Frost Dates and Growing Season

NOAA 1991-2020 normals for Dubois, 2.1 km from Dubois, elevation 6955 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Dubois. 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 25, first September 16

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 15	Jun 6	Jun 1	May 28	May 25	May 22	May 19	May 16	May 11
24°F	May 23	May 19	May 15	May 12	May 10	May 7	May 5	May 2	Apr 30
20°F	May 13	May 8	May 4	May 1	Apr 30	Apr 27	Apr 24	Apr 20	Apr 16
16°F	May 3	Apr 29	Apr 25	Apr 21	Apr 17	Apr 14	Apr 11	Apr 7	Apr 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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	–	–	–	–	–	–	–	–	–
32°F	–	–	–	–	–	–	–	–	–
28°F	Sep 1	Sep 5	Sep 10	Sep 13	Sep 16	Sep 19	Sep 23	Sep 27	Oct 1
24°F	Sep 14	Sep 19	Sep 23	Sep 26	Sep 29	Oct 1	Oct 4	Oct 8	Oct 13
20°F	Sep 21	Sep 27	Oct 1	Oct 5	Oct 8	Oct 12	Oct 15	Oct 20	Oct 25
16°F	Oct 1	Oct 7	Oct 12	Oct 16	Oct 20	Oct 24	Oct 27	Oct 31	Nov 4

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	67	60	53	48	42	38	34	29	23
32°F	97	90	85	79	74	69	64	58	48
28°F	132	126	121	116	112	107	102	95	87
24°F	159	152	148	143	139	136	132	127	122
20°F	181	173	169	165	160	155	150	144	137
16°F	206	198	193	187	182	178	173	167	158

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: 8,930
Cooling degree days, base 65°F: 32
Growing degree days, base 40°F: 2,533
Growing degree days, base 45°F: 1,691
Growing degree days, base 50°F: 1,024
Growing degree days, base 55°F: 513
Growing degree days, base 60°F: 175

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	1,263	0	0
February	1,128	0	0
March	1,039	0	0
April	832	0	4
May	589	0	48
June	317	2	168
July	129	19	357
August	165	10	314
September	397	1	119
October	746	0	14
November	1,037	0	1
December	1,288	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 2.1 km from Dubois. 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 USC00482715 (Dubois). Public domain.