Texas Gulf Coast
Port O'Connor Water Temperature
Pass Cavallo, San Antonio Bay, and back lakes you can only reach on high water.
That is about 6°F warmer than average for this time of year, and holding steady over the last two weeks. The October average here is 80°F.
Updated Saturday, October 3 — sea-surface temperature modeled for Port O'Connor by Open-Meteo.
Out in the open Gulf, NOAA buoy 42002 — 236 miles offshore — is reading 87°F. Deep water offshore runs cooler than the shallows in summer and warmer in winter, so it won't match the beach.
For swimming
Very warm
Bath-warm. Pleasant, though it stops being much relief from the heat of the day.
For fishing
Hot — fish the edges of the day
Early and late is the play. Through the middle of the day fish drop into deeper channels and passes where there's moving water and more oxygen.
The last two weeks
Daily average sea-surface temperature, °F.
Port O'Connor water temperature by month
Averaged from 3 years of daily sea-surface temperature (2023–2025). The range column is the coolest and warmest daily average recorded in that month over the period — a guide to how much any given year can differ, not a record high and low.
| Month | Average | Range | Swimming |
|---|---|---|---|
| January | 58°F | 52–66°F | Cold |
| February | 61°F | 57–67°F | Bracing |
| March | 67°F | 60–72°F | Bracing |
| April | 74°F | 70–79°F | Cool but comfortable |
| May | 81°F | 74–85°F | Warm |
| June | 86°F | 83–88°F | Very warm |
| July | 87°F | 85–88°F | Very warm |
| August | 88°F | 86–90°F | Bath water |
| September | 86°F | 81–89°F | Very warm |
| Octobernow | 80°F | 74–85°F | Warm |
| November | 73°F | 64–79°F | Cool but comfortable |
| December | 65°F | 59–71°F | Bracing |
Warmest on average in August at 88°F; coolest in January at 58°F.
The water at Port O'Connor
Port O'Connor sits at the hinge between Matagorda Bay and San Antonio Bay, with Pass Cavallo — a natural, unjettied pass that shifts its sand every season — draining the whole system to the Gulf. Behind Matagorda Island lies a maze of back lakes and shallow sand-and-grass flats where waders chase trophy trout in knee-deep water, and the ship channel jetties hold redfish, drum, and late-summer tarpon. Matagorda Island itself has no bridge and no road, so its beach, its birding, and its camping belong to whoever runs a boat across. Espiritu Santo Bay to the south is quieter and shallower and rewards anyone willing to pole or wade a long way from the ramp.
Matagorda Bay, San Antonio Bay & Pass Cavallo
What moves the water temperature here
The Gulf shelf off this coast is shallow, which is why the water swings so much more between summer and winter than open ocean at the same latitude does. Shallow water heats fast and gives that heat up fast: a single strong winter cold front can pull the inshore bays several degrees down in a couple of days, while the beaches a mile offshore barely move. Wind direction matters too — a sustained offshore breeze can pull cooler water up from below and drop the beach temperature noticeably in a morning.
Inshore bays, canals and flats run warmer than the beach through the summer and colder through the winter, for the same reason. The reading above is for the open water at Port O'Connor; expect the back bays to be a few degrees either side of it depending on the season.
Common questions
- What is the water temperature at Port O'Connor right now?
- The water at Port O'Connor is currently about 86°F (30°C). The October average here is 80°F.
- Is the water warm enough to swim at Port O'Connor in October?
- October averages 80°F at Port O'Connor, which most people would call warm. About as good as it gets — warm enough to stay in for hours without getting chilled.
- When is the water warmest at Port O'Connor?
- August is the warmest month on average at 88°F, and January the coolest at 58°F. 6 months of the year average 75°F or above.
- Why does the water temperature change so quickly here?
- The Gulf shelf off this coast is shallow, so it heats and cools far faster than deep open ocean. A strong winter cold front can pull the inshore water down several degrees in a couple of days, and a sustained offshore wind can drop beach temperatures in a single morning by pulling cooler water up from below.