The hottest month in Guernsey is July when the average maximum temperature is 20°, average temperature is 17° and average minimum temperature is 14°.
The coolest month in Guernsey is February when the average maximum temperature is 8°, average temperature is 6° and average minimum temperature is 5°.
The longest days in Guernsey are in June, with an average of 16.2 hours of daylight per day. December has the shortest days with an average of 8.2 hours of daylight per day.
The sunniest days in Guernsey are in June which has the most hours of sunshine per day with an average of 8.3 hours of sunshine per day, making it a sunny month with few clouds. December has the least sunshine with an average of 1.8 hours of sunshine per day, making it not a particularly sunny month.
The ultraviolet index is the highest in June when it reaches 7.9 and lowest in December when it reaches 0.6.
An ultraviolet index reading of 8 to 10 indicates a very high risk of harm from unprotected sun exposure. Unprotected skin risks burning in less than 15 minutes. Take extra precautions because unprotected skin and eyes will be damaged and can burn quickly. 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 Guernsey are found in August when they peak at 19° and lowest in March when they dip to 9°.
The sea is best for swimming between June and December when the temperature is above 14° which is cold for swimming, a full wet suit is required to spend any length of time in the sea.
The wettest month in Guernsey is December with 0.9cm of rain and January has the most days of rain with 21.7 days with some rain, a very wet time to visit the beach.
The driest month in Guernsey is May with 0.3cm of rain and June has the fewest days of rain with 12.8 days with some rain, a slightly wet time to visit the beach.
The most humid month in Guernsey is August with a dew point (an indicator of humidity) of 15° which is comfortable for everyone.
The least humid month in Guernsey is February with a dew point of 6° which is a bit dry for some.
The most windy month in Guernsey is December when the average maximum windspeed is 37kmh and the average wind speed is 25kmh.
The least windy month in Guernsey is August when the average maximum windspeed is 27kmh and the average wind speed is 18kmh.