The hottest month in Cayo Guillermo Beach is August when the average maximum temperature is 32°, average temperature is 28° and average minimum temperature is 25°.
The coolest month in Cayo Guillermo Beach is January when the average maximum temperature is 26°, average temperature is 23° and average minimum temperature is 20°.
The longest days in Cayo Guillermo Beach are in June, with an average of 13.5 hours of daylight per day. December has the shortest days with an average of 10.8 hours of daylight per day.
The sunniest days in Cayo Guillermo Beach are in April which has the most hours of sunshine per day with an average of 9.3 hours of sunshine per day, making it a sunny month with few clouds. December has the least sunshine with an average of 7.1 hours of sunshine per day, making it a quite sunny month with some cloud cover.
The ultraviolet index is the highest in May when it reaches 12.7 and lowest in December when it reaches 6.2.
An ultraviolet index reading above 11 indicates an extreme risk of harm from unprotected sun exposure. Unprotected skin risks burning in less than 10 minutes. Take all precautions because unprotected skin and eyes can burn in minutes. Tanning will be safest before 10am and after 4pm but only with a good application of sun screen. For those with sensitive skin stay in the shade and wear protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. Generously apply broad spectrum SPF 30+ sunscreen every 2 hours, even on cloudy days. Watch out for relections from water that may increase ultraviolet exposure.
The warmest sea water temperatures in Cayo Guillermo Beach are found in September when they peak at 29° and lowest in March when they dip to 27°.
The sea is excellent for swimming all year round as the water temperature is very warm and ideal for relaxing and swimming for the whole day.
The most humid month in Cayo Guillermo Beach is August with a dew point (an indicator of humidity) of 25° which is very uncomfortable and fairly oppressive unless you are on a beach. At night you would most likely require airconditioning.
The least humid month in Cayo Guillermo Beach is January with a dew point of 19° which is somewhat uncomfortable for most people in cities but fine on a beach.
The most windy month in Cayo Guillermo Beach is March when the average maximum windspeed is 30kmh and the average wind speed is 17kmh.
The least windy month in Cayo Guillermo Beach is October when the average maximum windspeed is 24kmh and the average wind speed is 13kmh.