The hottest month in Key Biscayne is August when the average maximum temperature is 33°, average temperature is 29° and average minimum temperature is 26°.
The coolest month in Key Biscayne is January when the average maximum temperature is 25°, average temperature is 21° and average minimum temperature is 16°.
The longest days in Key Biscayne are in June, with an average of 13.7 hours of daylight per day. December has the shortest days with an average of 10.5 hours of daylight per day.
The sunniest days in Key Biscayne are in April which has the most hours of sunshine per day with an average of 9.6 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 July when it reaches 12.4 and lowest in December when it reaches 5.3.
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 Key Biscayne are found in July when they peak at 29° and lowest in January when they dip to 23°.
The sea is best for swimming between May and December when the temperature is above 26° which is very warm and ideal for relaxing and swimming for the whole day.
The wettest month in Key Biscayne is June with 336.1cm of rain and September has the most days of rain with 23 days with some rain, a very wet time to visit the beach.
The driest month in Key Biscayne is January with 33.5cm of rain and February has the fewest days of rain with 7.2 days with some rain, a slightly wet time to visit the beach.
The most humid month in Key Biscayne 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 Key Biscayne is January with a dew point of 17° which is OK for most but slightly uncomfortable for some.
The most windy month in Key Biscayne is June when the average maximum windspeed is 30kmh and the average wind speed is 12kmh.
The least windy month in Key Biscayne is December when the average maximum windspeed is 26kmh and the average wind speed is 12kmh.