Saint Lucia, an island of the Lesser Antilles belonging to the Commonwealth, with Castries as the capital, has a tropical climate, hot all year round, with a relatively cool, dry season from January to mid-April and a hot, humid and rainy season from mid-June to November. In the former period, the northeast trade winds, constant winds typical of tropical climates, blow steadily and with moderate intensity, while in the latter period, these winds are more irregular, and may have some breaks, increasing the feeling of sultriness. Between them, there are two transitional periods: from December to early January (when the northeast wind starts to blow, the temperature decreases a bit, and the weather improves) and from mid-April to Mid-June (when both the temperature and the frequency of downpours gradually increase).
Here are the average temperatures in Vieux Fort. As you can see, there are little variations between the coolest and the warmest period.
Vieux Fort - Average temperatures
Min (°C)232324242525252525252424
Max (°C)292929303131313131313029
Min (°F)737375757777777777777575
Max (°F)848484868888888888888684

Rainfall in Saint Lucia varies depending on altitude and location; in fact, the inland elevations receive more rainfall than the coast, and the areas closest to the mountains are rainier than the more distant ones. However, the rains follow the same pattern, and are more frequent and abundant from July to November and less frequent and shorter from February to April. In Vieux Fort, which is located on the south coast, in the driest point, 1,400 millimeters (55 inches) of rain fall per year, of which more than 100 mm (4 in) fall per month from July to December. The least rainy months are February and March, with approximately 50/60 mm (2/2.4 in) per month on average. Other coastal areas, such as that of Castries, receive more rain, about 2,000 mm (79 in) per year, although the pattern is the same.
Here is the average precipitation in Castries.
Castries - Average precipitation

In inland areas, on the slopes of Mount Gimie, 950 meters (3,120 feet) high, the rains are even more abundant, in fact, they are covered with rainforests.
Throughout the year, the rains occur especially in the form of downpours or thunderstorms, which could be intense, but generally do not last long, so they do not reduce too much the sunshine hours; sometimes, however, there may be a more intense wave of bad weather.
In fact, the amount of sunshine is good all year round, at least along the coasts, as can be seen in the following table.
Castries - Sunshine

Saint Lucia

The sea in Saint Lucia is warm enough to swim in throughout the year: the water temperature ranges from 26 °C (79 °F) in February and March to 29 °C (84 °F) in September and October.
St. Lucia - Sea temperature
Temp (°C)272626272828282829292827
Temp (°F)817979818282828284848281


Saint Lucia can be affected by tropical storms and cyclones, called hurricanes in the Caribbean area, which may pass over the island from June to November, though they are most likely from August to October. A hurricane that caused serious damage to the island was Allen in August 1980.

Best Time

The best time to visit Saint Lucia is from December to April, since it is the coolest and the least rainy period of the year, and especially from February to April, which is the dryest of all.

What to pack

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