Cameron County Frost Dates and Growing Season

NOAA 1991-2020 normals for Port Isabel Cameron AP, 10.8 km from Cameron County, elevation 19 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Port Isabel Cameron AP. 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 35 percent of years at Port Isabel Cameron AP, so there is no typical freeze season.

Median at 36°F: last January 22, first December 29
Median at 32°F: last January 8, 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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	Feb 26	Feb 15	Feb 4	Jan 28	Jan 22	Jan 14	Jan 7	Jan 1	Dec 20
32°F	Feb 7	Jan 30	Jan 22	Jan 13	Jan 8	Jan 5	Jan 1	Dec 24	Dec 16
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 1	Dec 8	Dec 16	Dec 22	Dec 29	Jan 3	Jan 7	Jan 15	Jan 31
32°F	Dec 10	Dec 18	Dec 25	Dec 31	Jan 4	Jan 7	Jan 13	Jan 24	Feb 4
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	364	356	348	340	333	325	314	300
32°F	365	365	365	365	365	365	359	349	335
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: 80% of years
32°F or colder: 35% of years
28°F or colder: 7% 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: 527
Cooling degree days, base 65°F: 4,140
Growing degree days, base 40°F: 12,741
Growing degree days, base 45°F: 10,923
Growing degree days, base 50°F: 9,122
Growing degree days, base 55°F: 7,363
Growing degree days, base 60°F: 5,691

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	177	55	358
February	103	96	420
March	39	189	616
April	7	314	758
May	0	484	949
June	0	577	1,028
July	0	623	1,088
August	0	632	1,097
September	0	529	980
October	4	374	835
November	50	180	582
December	147	85	412

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 10.8 km from Cameron County. 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 USW00012957 (Port Isabel Cameron AP). Public domain.