Seeley Lake Frost Dates and Growing Season

NOAA 1991-2020 normals for Seeley Lake RS, 4.8 km from Seeley Lake, elevation 4100 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Seeley Lake RS. 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 23, first September 22

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 11	Jun 4	May 31	May 27	May 23	May 20	May 17	May 13	May 9
24°F	May 20	May 14	May 10	May 7	May 4	May 2	Apr 30	Apr 27	Apr 21
20°F	May 3	Apr 30	Apr 25	Apr 22	Apr 19	Apr 16	Apr 12	Apr 8	Apr 3
16°F	Apr 23	Apr 17	Apr 13	Apr 9	Apr 5	Apr 3	Mar 31	Mar 28	Mar 21

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 4	Sep 10	Sep 15	Sep 18	Sep 22	Sep 24	Sep 27	Sep 30	Oct 4
24°F	Sep 22	Sep 26	Sep 29	Oct 1	Oct 3	Oct 6	Oct 10	Oct 14	Oct 20
20°F	Oct 1	Oct 5	Oct 10	Oct 14	Oct 18	Oct 21	Oct 26	Oct 31	Nov 4
16°F	Oct 10	Oct 19	Oct 23	Oct 28	Oct 31	Nov 3	Nov 7	Nov 11	Nov 18

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	62	54	47	42	38	34	30	25	21
32°F	100	93	86	80	74	69	63	57	48
28°F	141	133	127	122	118	114	109	102	93
24°F	172	165	160	156	152	148	144	139	132
20°F	205	196	190	185	180	176	170	165	158
16°F	229	221	215	211	207	202	197	190	182

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: 8,563
Cooling degree days, base 65°F: 108
Growing degree days, base 40°F: 2,911
Growing degree days, base 45°F: 2,032
Growing degree days, base 50°F: 1,308
Growing degree days, base 55°F: 742
Growing degree days, base 60°F: 341

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	1,332	0	0
February	1,130	0	0
March	1,008	0	0
April	744	0	7
May	486	1	77
June	268	8	205
July	94	55	427
August	110	40	398
September	316	5	173
October	702	0	22
November	1,037	0	0
December	1,339	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 4.8 km from Seeley Lake. 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 USC00247448 (Seeley Lake RS). Public domain.