Atascadero climate

Atascadero Frost Dates and Growing Season

NOAA 1991-2020 normals for Paso Robles, 15.5 km from Atascadero, elevation 730 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Paso Robles. 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 March 15 and the first fall freeze around November 10, a growing season of about 238 days.

Median at 36°F
last April 18, first October 27
Median at 32°F
last March 15, first November 10
Median at 28°F
last February 9, first November 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.

Threshold10%20%30%40%50%60%70%80%90%
36°FMay 6Apr 30Apr 25Apr 21Apr 18Apr 13Apr 8Apr 3Mar 24
32°FApr 13Apr 6Mar 31Mar 25Mar 15Mar 8Feb 28Feb 24Feb 12
28°FMar 4Feb 26Feb 21Feb 14Feb 9Feb 3Jan 28Jan 18Jan 2
24°FFeb 12Feb 3Jan 29Jan 20Jan 11Jan 4Dec 31Dec 25Dec 13
20°FJan 26Jan 15Jan 10Jan 4Jan 1Dec 30Dec 25Dec 19Dec 11
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°FOct 12Oct 17Oct 21Oct 24Oct 27Oct 30Nov 2Nov 6Nov 12
32°FOct 23Oct 30Nov 1Nov 5Nov 10Nov 14Nov 18Nov 22Nov 29
28°FNov 4Nov 13Nov 18Nov 22Nov 26Nov 29Dec 2Dec 8Dec 19
24°FNov 21Nov 28Dec 1Dec 4Dec 8Dec 13Dec 21Jan 1Jan 10
20°FDec 2Dec 6Dec 12Dec 16Dec 20Dec 26Dec 31Jan 2Jan 11
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°F218208202196190186180173165
32°F275263254246238231224216206
28°F326315303295287280274266256
24°F365356345338334329323312300
20°F365365365365365363354346337
16°F365365365365365365365365364

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
85% of years
20°F or colder
39% of years
16°F or colder
8% 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
2,777
Cooling degree days, base 65°F
851
Growing degree days, base 40°F
7,210
Growing degree days, base 45°F
5,458
Growing degree days, base 50°F
3,887
Growing degree days, base 55°F
2,599
Growing degree days, base 60°F
1,591

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January526033
February412062
March3460145
April2417225
May12052397
June36135549
July10226680
August7234693
September26156581
October13340373
November3631124
December559025

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 15.5 km from Atascadero. 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 USC00046730 (Paso Robles). Public domain.