in december the weather usually is quite nice - whatever this means, as it depends on you, you like it hot (the temperature!!!) or a little cool??? in december it's mauritian summer, during day the temperature may go up to 35°. i enjoy it, because it's not too humid. usually there's some rain every day, a pretty heavy rain for a few minutes - then within a short time everything is dry again.
and do not bother too much about the cyclones. the last one that hit mauritius was "dina" in january 2002. mauritius is such a small island that is not hit by a cyclone several times a year! and if there is a cyclone, there will be warnings and instruction what to do.
enjoy your holiday!!!