Tujunga Frost Dates and Growing Season

NOAA 1991-2020 normals for Burbank Valley Pump Plt, 9.1 km from Tujunga, elevation 655 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Burbank Valley Pump Plt. 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 January 2 and the first fall freeze around December 26, a growing season of about 364 days.

Median at 36°F: last February 5, first December 12
Median at 32°F: last January 2, first December 26

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	Mar 10	Mar 1	Feb 23	Feb 14	Feb 5	Jan 29	Jan 18	Jan 9	Dec 31
32°F	Jan 31	Jan 17	Jan 10	Jan 5	Jan 2	Dec 30	Dec 25	Dec 19	Dec 11
28°F	–	–	–	–	–	–	–	–	–
24°F	–	–	–	–	–	–	–	–	–
20°F	–	–	–	–	–	–	–	–	–
16°F	–	–	–	–	–	–	–	–	–

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	Nov 23	Nov 30	Dec 4	Dec 8	Dec 12	Dec 16	Dec 20	Dec 26	Jan 3
32°F	Dec 5	Dec 11	Dec 16	Dec 21	Dec 26	Dec 30	Jan 1	Jan 6	Jan 18
28°F	–	–	–	–	–	–	–	–	–
24°F	–	–	–	–	–	–	–	–	–
20°F	–	–	–	–	–	–	–	–	–
16°F	–	–	–	–	–	–	–	–	–

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	345	334	324	315	308	300	290	281	268
32°F	365	365	365	365	364	358	350	342	330
28°F	365	365	365	365	365	365	365	365	365
24°F	365	365	365	365	365	365	365	365	365
20°F	365	365	365	365	365	365	365	365	365
16°F	365	365	365	365	365	365	365	365	365

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder: 98% of years
32°F or colder: 55% of years
28°F or colder: 3% of years
24°F or colder: 0% of years
20°F or colder: 0% of years
16°F or colder: 0% 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: 1,463
Cooling degree days, base 65°F: 1,287
Growing degree days, base 40°F: 8,949
Growing degree days, base 45°F: 7,127
Growing degree days, base 50°F: 5,340
Growing degree days, base 55°F: 3,699
Growing degree days, base 60°F: 2,324

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	288	2	190
February	250	5	185
March	201	14	282
April	127	33	356
May	65	67	467
June	13	145	582
July	0	285	750
August	0	329	794
September	4	265	711
October	39	118	544
November	160	23	315
December	316	1	165

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 9.1 km from Tujunga. 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 USC00041194 (Burbank Valley Pump Plt). Public domain.