The hottest month in Ishigaki Island is July when the average maximum temperature is 31°, average temperature is 29° and average minimum temperature is 28°.
The coolest month in Ishigaki Island is January when the average maximum temperature is 20°, average temperature is 18° and average minimum temperature is 17°.
The longest days in Ishigaki Island are in June, with an average of 13.6 hours of daylight per day. December has the shortest days with an average of 10.6 hours of daylight per day.
The sunniest days in Ishigaki Island are in May which has the most hours of sunshine per day with an average of 6.4 hours of sunshine per day, making it a quite sunny month with some cloud cover. December has the least sunshine with an average of 3.6 hours of sunshine per day, making it not a particularly sunny month.
The ultraviolet index is the highest in July when it reaches 12.9 and lowest in December when it reaches 5.9.
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 Ishigaki Island are found in July when they peak at 30° and lowest in February 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 most humid month in Ishigaki Island is August with a dew point (an indicator of humidity) of 26° 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 Ishigaki Island is January with a dew point of 14° which is comfortable for everyone.
The most windy month in Ishigaki Island is December when the average maximum windspeed is 40kmh and the average wind speed is 31kmh.
The least windy month in Ishigaki Island is May when the average maximum windspeed is 28kmh and the average wind speed is 21kmh.