Mississippi Coast
Bay St. Louis Water Temperature
A quiet bay, the long bridge across it, and the west end of this coast.
That is about 7°F warmer than average for this time of year, and cooling over the last two weeks. The October average here is 77°F.
Updated Saturday, October 3 — sea-surface temperature modeled for Bay St. Louis by Open-Meteo.
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.
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 |
| August | 90°F | 86–93°F | Bath water |
| September | 85°F | 80–89°F | Very warm |
| Octobernow | 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.
The water at Bay St. Louis
Bay St. Louis is the unhurried end of the Mississippi coast: an old town above the bay it is named for, a long bridge reaching across to Pass Christian, and a beach that never draws the crowds the towns east of here do. The bay and the bridge structure hold speckled trout, redfish, flounder and black drum, and the shallow marsh shorelines fish well on moving water once the heat backs off. Sailing, paddling and plain beach walking take up as much of the local calendar as fishing. Sitting at the western end of the coast puts this town nearest the freshwater influence coming out of Lake Borgne and the surrounding marsh, so water color swings quickly after heavy rain.
the bay, the bridge & the Sound
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 84°F (29°C). The October average here is 77°F.
- Is the water warm enough to swim at Bay St. Louis in October?
- October averages 77°F at Bay St. Louis, 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 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.