The hottest month in Cornwall is July when the average maximum temperature is 19°, average temperature is 16° and average minimum temperature is 13°.
The coolest month in Cornwall is February when the average maximum temperature is 9°, average temperature is 6° and average minimum temperature is 4°.
The longest days in Cornwall are in June, with an average of 16.4 hours of daylight per day. December has the shortest days with an average of 8.1 hours of daylight per day.
The sunniest days in Cornwall are in June which has the most hours of sunshine per day with an average of 7.5 hours of sunshine per day, making it a quite sunny month with some cloud cover. 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 7.7 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 Cornwall are found in August when they peak at 17° and lowest in February when they dip to 10°.
The sea is best for swimming between June and December when the temperature is above 13° which is very cold and bracing, it's not recommended you swim with out a full wet suit.
The wettest month in Cornwall is November with 2cm of rain and the most days of rain with 21.3 days with some rain, a very wet time to visit the beach.
The driest month in Cornwall is September with 0.4cm of rain and June has the fewest days of rain with 14.6 days with some rain, a slightly wet time to visit the beach.
The most humid month in Cornwall is August with a dew point (an indicator of humidity) of 15° which is comfortable for everyone.
The least humid month in Cornwall is February with a dew point of 6° which is a bit dry for some.
The most windy month in Cornwall is January when the average maximum windspeed is 35kmh and the average wind speed is 23kmh.
The least windy month in Cornwall is August when the average maximum windspeed is 26kmh and the average wind speed is 16kmh.