Visiting Mallorca in December would prove to be quite a cool experience, with an average temperature of 11 degrees C. Highs reach 16 degrees C and lows drop to 6 degrees C. Night time can be rather cold. The temperature of the sea is a chilly 7 degrees C, so sea bathing is off the holiday agenda. It is definitely the month for swimming in a heated pool. It rains for an average of 12 days in the month and there is only an average of two hours sun a day. Warm clothing should definitely be a part of everyoneâs holiday wardrobe in Mallorca in December, especially to wear in the evenings, and some waterproof clothing will come in handy too.