Two distinct seasons govern the Maldives.
Dry season (November–April), called Iruvai, is high season for tourism. Skies are mostly clear, the sea is flat, underwater visibility is at its best (often 30 metres-plus on the eastern reefs), and the trade winds are gentle. This is when to come if diving is the primary reason for the trip. Prices are at their highest from late December through January.
Wet season (May–October), called Hulhangu, brings the southwest monsoon, more frequent rain, and occasional rough seas. Underwater visibility drops a little, but conditions remain divable on most days. Mantas are more commonly seen on the eastern side of the atoll in this period as the currents reverse. Prices fall significantly outside of school holidays.
Best months overall: February and March for clear conditions, August and September for value and mantas. Avoid: the changeover periods in late April–May and October–November, when weather can be unpredictable.