Aransas Pass Frost Dates and Growing Season

NOAA 1991-2020 normals for Port Aransas, 12 km from Aransas Pass, elevation 12 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Port Aransas. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

A freeze (32°F or colder) happens in only 37 percent of years at Port Aransas, so there is no typical freeze season.

Median at 36°F: last January 28, first January 1
Median at 32°F: last January 16, first January 5

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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	Mar 3	Feb 22	Feb 13	Feb 2	Jan 28	Jan 21	Jan 15	Jan 6	Dec 26
32°F	Feb 23	Feb 4	Jan 28	Jan 23	Jan 16	Jan 7	Jan 1	Dec 28	Dec 19
28°F	–	–	–	–	–	–	–	–	–
24°F	–	–	–	–	–	–	–	–	–
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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	Dec 5	Dec 13	Dec 20	Dec 27	Jan 1	Jan 6	Jan 15	Jan 22	Feb 5
32°F	Dec 12	Dec 20	Dec 27	Dec 31	Jan 5	Jan 12	Jan 20	Jan 28	Feb 10
28°F	–	–	–	–	–	–	–	–	–
24°F	–	–	–	–	–	–	–	–	–
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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	365	365	355	347	339	331	321	311	300
32°F	365	365	365	365	365	365	358	346	328
28°F	365	365	365	365	365	365	365	365	365
24°F	365	365	365	365	365	365	365	365	365
20°F	365	365	365	365	365	365	365	365	365
16°F	365	365	365	365	365	365	365	365	365

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder: 77% of years
32°F or colder: 37% of years
28°F or colder: 9% of years
24°F or colder: 0% of years
20°F or colder: 0% 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: 833
Cooling degree days, base 65°F: 3,378
Growing degree days, base 40°F: 11,675
Growing degree days, base 45°F: 9,866
Growing degree days, base 50°F: 8,090
Growing degree days, base 55°F: 6,382
Growing degree days, base 60°F: 4,798

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	276	8	228
February	175	15	274
March	72	75	471
April	12	198	636
May	0	382	846
June	0	523	973
July	0	583	1,048
August	0	598	1,063
September	0	499	950
October	6	346	805
November	80	120	495
December	212	31	302

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 Aransas Pass. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00417170 (Port Aransas). Public domain.