Vejret i Charlotte Amalie (St Thomas) i december

December opens the dry season without being dry: regulars put it at about four and a half inches and warn that the month can still be wet, adding that a wet day here is not a wet day at home. Our row says 79.8mm across 11.9 days, seven millimetres apiece, under 29.6C over 23.3C. The payoff they name is specific - less rain means less runoff, so the bioluminescent bays are clearer and the glow stronger. The cost is the calendar: the festive season from about mid-December to early January is the island's high season, and air fares, hotels and car hire all climb with it. The record: humidity 82 percent, 10.1 hours of sun, a 18.8 kph wind and a 27.7C sea.

Regulars are specific this counts as prime season across the wider U.S. Virgin Islands, dry, sunny days the norm well before the real wet season and tropical storm risk return later in the year. Our row backs that hot, genuinely dry read, 28.5C reading as a hot 30C, over 22.9C nights feeling 23C, with rain light at 45.1mm across 9.6 days and a real 31 kph wind. Regulars are consistent water visibility for scuba and snorkeling stays genuinely clear and warm this time of year, a real draw for anyone timing a dive trip around it. The wind itself remains a steady daily feature, worth factoring into any boat trip regardless of how calm the morning looks. The sea sits at a warm, swimmable 26C. The record: 10.7 hours of sun, humidity 77 percent and AQI 40.

The season here ends at the end of April, and regulars say the weeks just after it are the value - fewer cruise ships in the harbour, lower room rates, the same weather. Our row gives 29.5C reading as 32C over 24.1C nights, with 46.4mm of rain across 7.4 days and a 27.4 kph trade wind that does most of the cooling. The sea is 26.9C. The recurring subject on this board is sargassum, and their answer is beach-specific rather than seasonal: one stretch gets nearly all of it, the big north-shore bay almost never does, and the resorts that rake in the morning are clear by the time you are up. The record: humidity 78 percent, 11.3 hours of sun and AQI 38.

January on St Thomas is high season in both senses: the weather is about as reliable as it gets, and the cruise ships are at their thickest, so how busy town feels on any given day is a question of how many are in port that morning. The water is a touch cooler than later in the year without being cold - a shorty is enough for diving - and the daytime breeze is what makes the heat comfortable. The one January variable regulars name is the Christmas Winds, which sometimes run on into the month and make a day or two properly windy. Our row has the trades at 29.1 kph, which is that breeze with a number on it. The record: 28.8C days that feel like 30C, 22.9C nights, 9.7 precipitation days carrying 38.6mm, 10.4 hours of sun and a 26.5C sea.

Forum posters describe September as feeling a bit hotter than other months mainly because the trade winds die down, though air and water temperatures otherwise stay fairly consistent year-round - ocean water in September is described as about as warm as it gets, a real plus for anyone prioritizing swimming. Posters characterize rain here as showers here and there rather than a genuine concern, with a full day of rain called rare even during this wetter stretch. September sits at the height of hurricane season, and while posters note no major direct hit since 1995, travel insurance is still commonly recommended given the real (if historically low) risk. The clear upside of visiting during this quieter month: fewer cruise ships, lighter crowds and easier movement around Charlotte Amalie generally.