Koh Phangan in December

December through May offers the driest weather and calmest seas. This is peak season, so expect crowds and higher prices, especially around Full Moon dates. January and February provide the sweet spot - dry weather, fewer tourists than December, and reasonable accommodation rates. Water temperatures stay perfect at 28°C. March gets hot (35°C+ daily) but remains mostly dry. Great for beach days if you can handle the heat. April pushes temperatures even higher but offers the year's best visibility for water activities. May marks the start of rainy season, but showers usually come in short bursts. You'll find the best deals on accommodation, and the island stays green and lush. Avoid September through November - monsoon season brings daily downpours, rough seas, and many businesses close. Some ferry routes get cancelled during storms. Full Moon Party dates determine everything. Accommodation prices triple, beaches become chaotic, and the entire island revolves around party logistics. Check lunar calendars before booking if you want to avoid or embrace the madness.