Phuket's weather is shaped by two seasonal monsoon systems, and understanding the basic mechanism explains most of what visitors actually notice through the year — more reliable for planning than a single-day weather forecast, which can't be checked more than a week or two out anyway.
The south-west monsoon (roughly May–October)
Brings the bulk of the island's rain and rougher seas, particularly affecting the west-facing coast where most tourist beaches sit. Rain tends to arrive in shorter, heavier bursts rather than constant all-day drizzle, leaving plenty of dry hours on most days even during the wettest months. July sits in the middle of this pattern — expect regular afternoon showers and daytime temperatures typically in the low-to-mid 30s°C, with humidity that makes it feel hotter than the number alone suggests.
The north-east monsoon (roughly November–February)
Brings Phuket's driest, most reliably sunny stretch — this is the core of high season for exactly that reason, and also when seas are calmest for island-hopping and diving. January is typically the driest month of the year, with daytime temperatures a touch more comfortable than the hotter months, generally low-to-mid 30s°C with lower humidity than green season.
Shoulder months
March-April and October-November sit between the two systems and can go either way — often good conditions with lower crowds than peak season, but less predictable than either core season. April is typically the hottest month overall, ahead of the rains properly setting in.
Checking an actual forecast
For a specific upcoming trip, a live weather forecast is more useful than seasonal averages once you're within a week or two of travel — general seasonal patterns are the right tool for choosing when to go, not for packing decisions the night before a specific date.
Why this matters for planning
See our best time to visit guide for how this translates into practical trip planning, and our Similan Islands guide for how the monsoon directly affects specific tour availability.