The climate of Saint Martin is tropical, hot and sunny all year round: the average daily temperature ranges from 25 °C (77 °F) in the coolest period, from January to March, to 28 °C (82 °F) in the hottest and most humid period, from June to October.
Here are the average temperatures of the capital, Marigot.
Marigot - Average temperatures
Min (°C)222223232425252526252423
Max (°C)282728282930303131302928
Min (°F)727273737577777779777573
Max (°F)828182828486868888868482

Saint Martin is an island of the Lesser Antilles, administratively divided between France and the Netherlands: here we are dealing with the French part, which is located on the northern side (on the Dutch side, we find instead Sint Maarten).
Usually, rainfall in Saint Martin is not very abundant, since it amounts to around 1,000 millimeters (40 inches) per year. February and March are the driest months, with 45/50 mm (1.8/2 in) of rain per month. The rains, which occur in the form of downpours or thunderstorms, are quite irregular, however, they usually increase from August to November.
Here is the average precipitation.
Marigot - Average precipitation

The amount of sunshine is good all year round, at least along the coasts, as can be seen in the following table.
Marigot - Sunshine


In Saint Martin, the sea is warm enough for swimming all year round, although it is a bit warmer in the summer months, as we can see in the following table.
Saint Martin - Sea temperature
Temp (°C)262626262728282829292827
Temp (°F)797979798182828284848281


In the period from June to November (but more likely from August to October), the island, like the rest of the Caribbean, can be hit by tropical storms and hurricanes.

Best Time

The best time to visit the island that includes Saint Martin is from December to April, and in particular, the months of February and March, which are the least rainy. In May, both temperature and moisture increase, but the rains are not yet too abundant, and the hurricane season has not yet begun. In summer, June and July are not as rainy as August and September, and have also a lower risk of hurricanes.

What to pack

All year round: bring light clothes of natural fabric, and possibly a light sweatshirt and a light raincoat for thunderstorms, especially from August to November. From December to March, you can add a light sweatshirt for the evening.
When going to the reef, you can bring snorkeling equipment, including water shoes or rubber-soled shoes.