High season begins in November and features higher percentage occupancy in hotels and higher prices for goods and services. The weather is generally clear and sunny. The coolest weather is in late December through early January. Peak high season is the Christmas-New Year period. It's crowded and more expensive.
Low season features wind predominantly from the southwest.
Storms which originate in Antarctica, pass by Sumatra on the way to Phuket. There are periods of one or two weeks during which it rains at least a little on most days. These are actually prime kayaking conditions. Cloudy days are cooler, making paddling more comfortable. Conditions often change by the hour.