Since Mozambique is primarily a beach destination, the weather is ultimately what determines the best time to visit. The main season is from March to November.
Some lodges may close in November for a month while others close in January/February depending on the rains. Generally November to February are the wet months where the weather ranges from very hot and humid to quite cold and grey. October can be pretty scorching just before the onset of the rains.
Mozambique is a long-thin country so the weather will vary a little between the north and the south.