Last updated: June 18, 2025
In September, the average temperature in St. Thomas, Canada hovers around 18°C (65°F), creating a pleasant atmosphere for residents and visitors alike. However, temperatures can fluctuate, with a minimum of 5°C (42°F) and a maximum reaching up to 29°C (85°F). Expect 82 mm (3.2 in) of precipitation spread over about 10 days, contributing to an average humidity level of 81%. Whether you're exploring the outdoors or enjoying cozy indoor activities, this month offers a comfortable climate for all!
In September in St. Thomas, the average temperature is 18°C (65°F). Maximums can reach 29°C (85°F), and minimums can be as low as 5°C (42°F). This makes St. Thomas an ideal destination for travelers seeking mild weather and pleasant outdoor activities.
In St. Thomas in September, the total precipitation amount is 82 mm (3.2 in) observed over a span of 10 days.
In St. Thomas in September, humidity is 81%. With an average temperature of 18°C (65°F), this humidity feels like a thick blanket wrapping around you, making every step feel heavier and the air thick and sultry—a challenging environment for traveling.
In St. Thomas in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in St. Thomas.
UV Risk Categories
Weather in St. Thomas varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in St. Thomas, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -3°C (27°F) | 76 mm (3.0 inches) | 90% | moderate |
| February Weather | -3°C (27°F) | 79 mm (3.1 inches) | 90% | moderate |
| March Weather | 1°C (34°F) | 81 mm (3.2 inches) | 87% | moderate |
| April Weather | 6°C (43°F) | 106 mm (4.2 inches) | 87% | very high |
| May Weather | 13°C (55°F) | 99 mm (3.9 inches) | 82% | very high |
| June Weather | 19°C (66°F) | 93 mm (3.7 inches) | 81% | very high |
| July Weather | 22°C (72°F) | 91 mm (3.6 inches) | 79% | very high |
| August Weather | 22°C (71°F) | 96 mm (3.8 inches) | 80% | very high |
| September Weather | 18°C (65°F) | 82 mm (3.2 inches) | 81% | very high |
| October Weather | 12°C (55°F) | 123 mm (4.9 inches) | 84% | high |
| November Weather | 5°C (41°F) | 94 mm (3.7 inches) | 88% | moderate |
| December Weather | 1°C (34°F) | 77 mm (3.0 inches) | 87% | low |