Brentwood climate

Brentwood Frost Dates and Growing Season

NOAA 1991-2020 normals for Brentwood, 4.8 km from Brentwood, elevation 707 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Brentwood. 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 April 15 and the first fall freeze around October 26, a growing season of about 193 days.

Median at 36°F
last April 28, first October 18
Median at 32°F
last April 15, first October 26
Median at 28°F
last April 2, first November 3

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°FMay 15May 8May 4May 1Apr 28Apr 25Apr 21Apr 17Apr 11
32°FMay 4Apr 28Apr 23Apr 19Apr 15Apr 11Apr 8Apr 4Mar 31
28°FApr 18Apr 13Apr 8Apr 5Apr 2Mar 31Mar 28Mar 23Mar 17
24°FApr 7Apr 2Mar 30Mar 25Mar 21Mar 18Mar 14Mar 9Mar 2
20°FMar 28Mar 22Mar 17Mar 14Mar 10Mar 5Mar 1Feb 25Feb 14
16°FMar 17Mar 10Mar 4Feb 28Feb 24Feb 18Feb 12Feb 5Jan 29

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°FOct 4Oct 9Oct 12Oct 15Oct 18Oct 20Oct 22Oct 25Oct 28
32°FOct 13Oct 18Oct 21Oct 23Oct 26Oct 28Oct 30Nov 1Nov 5
28°FOct 23Oct 27Oct 30Nov 1Nov 3Nov 5Nov 8Nov 12Nov 17
24°FNov 1Nov 4Nov 6Nov 9Nov 12Nov 15Nov 19Nov 25Dec 1
20°FNov 7Nov 12Nov 16Nov 20Nov 26Dec 1Dec 4Dec 8Dec 17
16°FNov 17Nov 25Nov 30Dec 4Dec 9Dec 14Dec 23Dec 30Jan 8

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°F192185179174170166162157150
32°F214207202197193189184179170
28°F239230223219215211206201193
24°F263254247242237232228222214
20°F291281274267263256250244235
16°F326313305298291284278270260

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
3,983
Cooling degree days, base 65°F
1,421
Growing degree days, base 40°F
7,056
Growing degree days, base 45°F
5,623
Growing degree days, base 50°F
4,336
Growing degree days, base 55°F
3,212
Growing degree days, base 60°F
2,243

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January866020
February687130
March532594
April26030257
May83110494
June4292738
July0398863
August2358821
September30187608
October21938304
November530276
December771031

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 Brentwood. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00401039 (Brentwood). Public domain.