Ladera climate

Ladera Frost Dates and Growing Season

NOAA 1991-2020 normals for Palo Alto, 7 km from Ladera, elevation 25 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Palo Alto. 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 February 1 and the first fall freeze around December 7, a growing season of about 310 days.

Median at 36°F
last March 11, first November 21
Median at 32°F
last February 1, first December 7
Median at 28°F
last January 4, first December 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.

Threshold10%20%30%40%50%60%70%80%90%
36°FApr 15Apr 6Mar 28Mar 18Mar 11Mar 4Feb 27Feb 20Feb 5
32°FMar 4Feb 24Feb 14Feb 7Feb 1Jan 25Jan 16Jan 7Dec 28
28°FFeb 17Feb 2Jan 21Jan 10Jan 4Dec 31Dec 28Dec 24Dec 15
24°FFeb 14Feb 3Jan 7Jan 1Dec 30Dec 25Dec 21Dec 17Dec 9
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.

Threshold10%20%30%40%50%60%70%80%90%
36°FNov 3Nov 9Nov 13Nov 17Nov 21Nov 24Nov 29Dec 1Dec 8
32°FNov 20Nov 26Dec 1Dec 3Dec 7Dec 11Dec 16Dec 25Jan 6
28°FDec 3Dec 7Dec 11Dec 16Dec 22Dec 27Jan 1Jan 8Jan 25
24°FDec 7Dec 12Dec 16Dec 20Dec 28Dec 31Jan 2Feb 1Feb 12
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.

Threshold10%20%30%40%50%60%70%80%90%
36°F292280269261252244235226214
32°F347335328320310303293283272
28°F365365365365358350343334318
24°F365365365365365365365365365
20°F365365365365365365365365365
16°F365365365365365365365365365

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
96% of years
28°F or colder
60% of years
24°F or colder
13% of years
20°F or colder
1% 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
2,733
Cooling degree days, base 65°F
364
Growing degree days, base 40°F
6,761
Growing degree days, base 45°F
4,983
Growing degree days, base 50°F
3,364
Growing degree days, base 55°F
2,034
Growing degree days, base 60°F
1,032

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January515034
February392070
March3251153
April2347226
May13624354
June4765468
July1594544
August1678527
September3574489
October13820348
November3570117
December524035

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 7 km from Ladera. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00046646 (Palo Alto). Public domain.