Map from Google - Saint_Martin

The climate of Saint Martin is tropical, hot and sunny all year round: the average daily temperature goes 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, which goes from June to September.
Saint Martin is an island of the Lesser Antilles, divided administratively between France and the Netherlands: the French side we are dealing with here is the northern one, with Marigot as the capital.
Here are the average temperatures of Marigot.
Average temperatures - Marigot
Min (°C)222223232425252526252423
Max (°C)282728282930303131302928
Min (°F)727273737577777779777573
Max (°F)828182828486868888868482

The rains in Saint Martin are generally not very abundant, since they amount to around 1,000 millimetres (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 downpour or thunderstorm, are quite irregular, experiencing however an increase from August to November.
Here is the average precipitation.
Average precipitation - Marigot
Prec. (mm)755045801007085115120100115901045

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


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

When to go

The best time to visit the island goes from December to April, and in particular February and March, which are the least rainy months. In May, heat and moisture increase, but the rains are not yet too abundant, and we are still out of the hurricane season. In summer, June and July are less rainy than August and September, and also have a lower risk of hurricanes.

What to pack

All year round: light clothes of natural fabric, possibly a light sweatshirt and a light raincoat for thunderstorms, especially from August to November; a light sweater or sweatshirt for the evening from December to March.
For the reef, equipment for snorkeling, water shoes or rubber soled shoes.