March in Cayo Guillermo is the sunniest month of the year. In March, the weather in Cayo Guillermo is typically warm. Average daily high temperature in March is about 25 degrees above zero. On average, Cayo Guillermo has 23 sunny, 6 partly cloudy, and 2 rainy days in March. The rains are usually light. March as well as February and April is considered the most comfortable time to visit Cayo Guillermo.