St. Barts (Saint Barthélemy) features a tropical maritime climate that is consistently warm, yet marked by subtle seasonal shifts that define the local lifestyle. Unlike larger Caribbean islands with dramatic mountain-induced rainfall, St. Barts’ small scale (just 9.6 square miles) and lack of high peaks result in a relatively dry environment where the sun is the dominant force.
The Seasonal Rhythm
Locals generally divide the year into two primary seasons based on rainfall and humidity rather than drastic temperature changes.
- The Lent (December to May): Known as the dry season, this is defined by clear skies and refreshing breeze. Temperatures typically hover between 72°F (22°C) and 84°F (29°C). This period is the most stable, with the least amount of rainfall and lower humidity.
- The Wintering (June to November): This is the warmer, more humid period. Daytime highs can reach 90°F (32°C). While the name suggests cold, it refers to the "wintering" of the trades, where the winds become less reliable and tropical showers more frequent, particularly in the late afternoon.
Daily Profiles and Trade Winds
The island is famously cooled by the Alizés (northeastern trade winds). These constant breezes are the island’s natural air conditioning.
- Morning: Most days begin with brilliant sunshine. Between January and March, these mornings can feel nearly "brisk" by Caribbean standards, often requiring a light layer before the sun climbs.
- Afternoon: In the wet season, short, intense tropical showers are common. Known as "liquid sunshine," these bursts rarely last more than 15-20 minutes and are usually followed by immediate sunlight.
- Evening: The sunset brings a mild drop in temperature. Nights are rarely cold; even in the heart of "winter," temperatures seldom dip below 70°F (21°C).
Microclimates and Coastal Variations
Despite its small size, St. Barts has distinct microclimates created by its hilly terrain.
- The Windward Side (East/North): Beaches like Toiny and Grand Fond are directly exposed to the Atlantic trade winds. This area feels significantly cooler and moves more air, making it popular for those who prefer a constant breeze.
- The Leeward Side (West/South): The capital, Gustavia, and beaches like Shell Beach are sheltered by the island’s hills. Here, the air can feel stiller and the heat more oppressive during the peak of the day, as the hills block the cooling Alizés.
- The Hills (Morne de Vitet): At the island’s highest point, the air is slightly thinner and cooler. Houses perched here often forgo artificial cooling entirely, relying on the elevated breeze.
Severe Weather and Historical Context
St. Barts is located within the Atlantic hurricane belt. The official season runs from June to November, with the highest probability of activity in September and October. Historically, the island is resilient; significant events like Hurricane Irma (2017) changed the landscape of local architecture, leading to more reinforced concrete structures and specialized storm shutters that are seamlessly integrated into luxury villa designs.
The "Feel" of the Island
The weather in St. Barts is experienced through its UV intensity and humidity. The sun at this latitude is exceptionally strong; even on a breezy day where the air feels cool, the sun can burn skin quickly. Humidity averages around 75%, but because of the steady winds, it rarely feels as "heavy" as in the rainforest-dense islands of the southern Caribbean.
Locals adapt by timing their outdoor activities for the early morning or late afternoon, often closing their homes during the midday heat to keep interiors cool through thermal mass and strategic cross-ventilation.