Terra Bella climate

Terra Bella Frost Dates and Growing Season

NOAA 1991-2020 normals for Porterville, 12 km from Terra Bella, elevation 393 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Porterville. 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 20 and the first fall freeze around December 13, a growing season of about 330 days.

Median at 36°F
last February 26, first November 28
Median at 32°F
last January 20, first December 13
Median at 28°F
last December 31, first December 23

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 7Mar 30Mar 16Mar 6Feb 26Feb 19Feb 10Feb 3Jan 25
32°FFeb 22Feb 6Jan 31Jan 26Jan 20Jan 14Jan 7Jan 1Dec 25
28°FJan 22Jan 17Jan 10Jan 4Dec 31Dec 29Dec 24Dec 19Dec 13
24°FJan 10Jan 5Dec 31Dec 29Dec 26Dec 20Dec 17Dec 14Dec 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 10Nov 17Nov 21Nov 24Nov 28Dec 1Dec 3Dec 7Dec 14
32°FNov 26Dec 1Dec 5Dec 9Dec 13Dec 16Dec 21Dec 28Jan 6
28°FDec 4Dec 11Dec 14Dec 19Dec 23Dec 28Jan 1Jan 5Jan 13
24°FDec 8Dec 14Dec 17Dec 20Dec 24Dec 28Dec 31Jan 2Jan 8
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°F312297289282273264254244230
32°F361348340336330322314304289
28°F365365365365365358351344336
24°F365365365365365365365365362
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
91% of years
28°F or colder
48% of years
24°F or colder
11% 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
1,966
Cooling degree days, base 65°F
2,237
Growing degree days, base 40°F
9,401
Growing degree days, base 45°F
7,615
Growing degree days, base 50°F
5,946
Growing degree days, base 55°F
4,478
Growing degree days, base 60°F
3,250

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January484063
February3130124
March21212272
April11753387
May31192626
June2380828
July05701,035
August0524989
September1370819
October47130549
November2666204
December496051

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 12 km from Terra Bella. 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 USC00047077 (Porterville). Public domain.