Key West is warmest in August, averaging 30° by day and 29° at night. The wettest month is September with 396 mm, and the year brings about 2089 mm in total.
Month by month
| Month | High | Low | Rain | Sea | Daylight | Good for |
|---|---|---|---|---|---|---|
| January | 24° | 21° | 37 mm | 23° | 10.6 h | Sightseeing |
| February | 24° | 22° | 48 mm | 23° | 11.2 h | Sightseeing |
| March | 25° | 23° | 43 mm | 25° | 11.8 h | Beach weather |
| April | 26° | 25° | 87 mm | 26° | 12.6 h | Beach weather |
| May | 28° | 26° | 167 mm | 28° | 13.2 h | Mild |
| June | 29° | 28° | 369 mm | 29° | 13.5 h | Rainy season |
| July | 30° | 29° | 233 mm | 31° | 13.4 h | Rainy season |
| August | 30° | 29° | 332 mm | 31° | 12.9 h | Rainy season |
| September | 30° | 29° | 396 mm | 30° | 12.1 h | Rainy season |
| October | 28° | 27° | 167 mm | 28° | 11.4 h | Mild |
| November | 26° | 25° | 117 mm | 26° | 10.8 h | Mild |
| December | 24° | 23° | 93 mm | 24° | 10.5 h | Sightseeing |
High and low are average daily maximum and minimum, rain is typical monthly total, sea is the average surface temperature, daylight is the hours between sunrise and sunset mid-month. Climate normals from NASA POWER and NOAA MUR — averages, not promises.
When to go
Beach weather: March and April — highs around 26°, nights no colder than 23°, and at most 87 mm of rain in a month. The sea sits at 25–26° then.
Walking the city: January, February and December — highs of 24–24° and no more than 93 mm of rain a month.
Wet season: June, July, August and September — up to 396 mm in a single month.