Mississippi Coast
Bay St. Louis Water Temperature
the bay, the bridge & the Sound
That is right about average for this time of year, and warming over the last two weeks. The August average here is 90°F.
Updated Wednesday, August 19 — sea-surface temperature modeled for Bay St. Louis by Open-Meteo.
For swimming
Bath water
Warmer than a heated pool. No cooling effect at all, and warm water like this holds less oxygen for the fish.
For fishing
Too hot for a midday bite
Water this warm carries noticeably less oxygen. Dawn is the bite and it's often over by mid-morning; the deeper passes and cuts hold the most life.
The last two weeks
Daily average sea-surface temperature, °F.
Bay St. Louis 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 | 53°F | 47–61°F | Cold |
| February | 58°F | 52–68°F | Cold |
| March | 65°F | 58–74°F | Bracing |
| April | 73°F | 67–81°F | Cool but comfortable |
| May | 81°F | 73–86°F | Warm |
| June | 87°F | 83–91°F | Very warm |
| July | 90°F | 89–92°F | Bath water |
| Augustnow | 90°F | 86–93°F | Bath water |
| September | 85°F | 80–89°F | Very warm |
| October | 77°F | 71–84°F | Warm |
| November | 69°F | 60–77°F | Cool but comfortable |
| December | 59°F | 52–65°F | Cold |
Warmest on average in July at 90°F; coolest in January at 53°F.
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 Bay St. Louis; 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 Bay St. Louis right now?
- The water at Bay St. Louis is currently about 91°F (33°C). The August average here is 90°F.
- Is the water warm enough to swim at Bay St. Louis in August?
- August averages 90°F at Bay St. Louis, which most people would call bath water. Warmer than a heated pool. No cooling effect at all, and warm water like this holds less oxygen for the fish.
- When is the water warmest at Bay St. Louis?
- July is the warmest month on average at 90°F, and January the coolest at 53°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.