USDA Hardiness Zone 10a
Frost Dates for 78578 — Port Isabel, Texas
NOAA 1991–2020 normals from Port Isabel, TX (17 ft), 4 miles west.
Updated
Frost is not a yearly event in Port Isabel: a night at or below 32°F came in 34% of the winters of 1991–2020 at Port Isabel, TX, and a 36°F night, cold enough for frost on exposed leaves, in 76%. There is no reliable "last frost date" here; most years have none.
- Winters with a freeze
- 34%
- Winters with 36°F
- 76%
- Coldest month low
- 52°F
- Hardiness zone
- 10a
32°F or below, 1991–2020
frost possible on leaves
average, January
30 to 35°F (-1.1 to 1.7°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 5%
- Snow per year
- 0.2"
median, 1991–2020
median, 1991–2020
1 of 20 observed
NOAA normal
Frost risk by date in Port Isabel
At Port Isabel, TX, 4 miles west of Port Isabel, 34% of the winters of 1991–2020 had at least one night at or below 32°F, 11% reached 28°F. Nights of 36°F, enough for frost on exposed leaves, are more common (76% of winters) and, when they come, fall between about December 25 and January 17. January is the month most likely to bring one: a 16% chance in a given year. 11 of the 351 other Texas stations behind this site's ZIP pages freeze in fewer than half of winters too.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F76% of yrs | Dec 18 | Dec 28 | Jan 1 | Jan 8 | Jan 17 | Jan 25 | Feb 2 | Feb 10 | Feb 24 |
| 32°F34% of yrs | too rare for a date | ||||||||
| 28°F11% of yrs | too rare for a date | ||||||||
| 24°F1% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F76% of yrs | Dec 1 | Dec 7 | Dec 15 | Dec 20 | Dec 25 | Dec 31 | Jan 3 | Jan 9 | Jan 31 |
| 32°F34% of yrs | too rare for a date | ||||||||
| 28°F11% of yrs | too rare for a date | ||||||||
| 24°F1% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Port Isabel, TX, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 78578 →Compare Port Isabel with another place →
Weather by month in Port Isabel
August is the warmest month at Port Isabel, TX, averaging 92°F by day and 77°F at night; January is the coldest at 69°F and 52°F. From February to November the chance of a 32°F night stays under 10% each month.
Warmth for growing adds up to 8,800 growing degree days a year (base 50°F), more than at 95% of the 351 Texas stations. 45% of them (3,939) have built up by the end of June, and August adds the most, 1,071. Precipitation totals 29.0 inches a year, most in September (6.2") and least in February (1.2"); May to September bring 55% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 69 | 52 | 1.5 | 16% | <1 | 336 |
| Feb | 72 | 56 | 1.2 | 5% | <1 | 405 |
| Mar | 76 | 61 | 1.7 | 0% | <1 | 573 |
| Apr | 81 | 67 | 1.6 | 0% | 0 | 717 |
| May | 86 | 73 | 2.4 | 0% | 0 | 911 |
| Jun | 90 | 76 | 3.1 | 0% | 0 | 996 |
| Jul | 91 | 77 | 2.3 | 0% | 0 | 1054 |
| Aug | 92 | 77 | 1.9 | 0% | 0 | 1071 |
| Sep | 89 | 74 | 6.2 | 0% | 0 | 936 |
| Oct | 85 | 69 | 3.9 | 0% | 0 | 839 |
| Nov | 78 | 61 | 1.8 | 1% | <1 | 575 |
| Dec | 71 | 54 | 1.4 | 16% | <1 | 387 |
Monthly normals 1991–2020 at Port Isabel, TX (17 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Port Isabel Cameron Airport, TX, 8 miles northwest of Port Isabel, has a 32°F night in 35% of winters against 34% here, and the same coolest-month low, 52°F.
When it snows in Port Isabel, Texas
Measurable snow is rare here: only 1 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Port Isabel, TX, 3.8 miles away, so there is no typical first-snow date to plan around.
Where these figures come from
ZIP 78578 is 4 miles from Port Isabel, TX, which stands at 17 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 78578 in zone 10a, the band where the coldest night of the year averaged 30 to 35°F (-1.1 to 1.7°C) over 1991–2020; a zone describes winter lows, not frost dates.
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.