Port O'Connor climate

Port O'Connor Frost Dates and Growing Season

NOAA 1991-2020 normals for Port O'connor, 2.6 km from Port O'Connor, elevation 5 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Port O'connor. 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 4 and the first fall freeze around December 27, a growing season of about 323 days.

Median at 36°F
last February 20, first December 6
Median at 32°F
last February 4, first December 27
Median at 28°F
last January 27, first January 4

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°FMar 13Mar 6Mar 2Feb 26Feb 20Feb 13Feb 6Jan 30Jan 21
32°FMar 6Feb 28Feb 21Feb 10Feb 4Jan 30Jan 22Jan 9Dec 29
28°FMar 1Feb 19Feb 8Feb 2Jan 27Jan 16Jan 4Dec 28Dec 15
24°FMar 5Feb 21Feb 8Feb 1Jan 23Jan 6Jan 1Dec 23Dec 8
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 12Nov 20Nov 26Dec 1Dec 6Dec 10Dec 19Jan 1Jan 9
32°FNov 20Nov 30Dec 6Dec 16Dec 27Jan 2Jan 8Jan 20Feb 4
28°FNov 27Dec 9Dec 21Dec 28Jan 4Jan 12Jan 26Feb 4Feb 20
24°FNov 30Dec 16Dec 27Jan 1Jan 9Jan 24Feb 2Feb 17Mar 2
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°F328314306299291283274266255
32°F365354341331323315307298282
28°F365365365365364350334323310
24°F365365365365365365365365342
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
99% of years
32°F or colder
88% of years
28°F or colder
51% of years
24°F or colder
18% of years
20°F or colder
3% of years
16°F or colder
1% 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
908
Cooling degree days, base 65°F
3,301
Growing degree days, base 40°F
11,522
Growing degree days, base 45°F
9,712
Growing degree days, base 50°F
7,934
Growing degree days, base 55°F
6,230
Growing degree days, base 60°F
4,665

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January2925211
February19414252
March8771453
April16181615
May1374839
June0519969
July05811,046
August06091,074
September0507957
October5330790
November8785451
December22724277

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 2.6 km from Port O'Connor. 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 USC00417186 (Port O'connor). Public domain.