Potrero climate

Potrero Frost Dates and Growing Season

NOAA 1991-2020 normals for Campo, 13.6 km from Potrero, elevation 2630 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Campo. 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 30 and the first fall freeze around October 26, a growing season of about 174 days.

Median at 36°F
last June 3, first October 2
Median at 32°F
last April 30, first October 26
Median at 28°F
last April 2, first November 14

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°FJun 29Jun 20Jun 13Jun 7Jun 3May 29May 23May 15May 3
32°FJun 1May 19May 13May 4Apr 30Apr 25Apr 20Apr 16Apr 9
28°FApr 28Apr 17Apr 11Apr 6Apr 2Mar 28Mar 18Mar 2Feb 23
24°FMar 28Mar 10Feb 27Feb 19Feb 13Feb 5Jan 30Jan 16Dec 29
20°FFeb 24Feb 13Feb 3Jan 27Jan 16Jan 6Dec 28Dec 17Dec 8
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°FSep 2Sep 14Sep 23Sep 28Oct 2Oct 7Oct 12Oct 17Oct 23
32°FSep 30Oct 9Oct 15Oct 21Oct 26Oct 30Nov 2Nov 6Nov 12
28°FOct 22Nov 1Nov 4Nov 9Nov 14Nov 19Nov 24Dec 1Dec 5
24°FNov 11Nov 21Nov 29Dec 2Dec 5Dec 10Dec 15Dec 25Jan 8
20°FDec 1Dec 8Dec 13Dec 19Dec 27Jan 2Jan 12Jan 28Feb 13
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°F1551421321241181111039380
32°F207196189181174166157148135
28°F271255244235226218210201191
24°F344330316306297286276264249
20°F365365365365365349338328313
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
100% of years
28°F or colder
100% of years
24°F or colder
97% of years
20°F or colder
53% of years
16°F or colder
6% 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
2,869
Cooling degree days, base 65°F
912
Growing degree days, base 40°F
7,181
Growing degree days, base 45°F
5,437
Growing degree days, base 50°F
3,872
Growing degree days, base 55°F
2,587
Growing degree days, base 60°F
1,615

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January492059
February434057
March4000107
April2922175
May16326330
June5295494
July6268727
August4303764
September27177600
October14836356
November3342151
December518052

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 13.6 km from Potrero. 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 USC00041424 (Campo). Public domain.