March in Key West is the sunniest month of the year. In March, the weather in Key West is typically warm. Average daily high temperature in March is about 23 degrees above zero. On average, Key West has 27 sunny, 3 partly cloudy, and 1 rainy day in March. The rains are usually light. March as well as January, February, April, and November is considered the most comfortable time to visit Key West.