The weather in Samui in September is starting to get cooler as we enter the autumn and winter months. Average temperatures are still quite pleasant at 28°C/82°F and the average humidity is between 63% and 89%. Rainfall is a feature of about 11 days of the month, though generally only in light showers adding up to about 130mm of precipitation. Most days are generally fine, with the added bonus that, after the August school holiday crowds, you can generally enjoy quiet beaches and attractions. Diving conditions are very good, with the clear water full of exciting marine life, average water temperatures of 28°C/82°F, mostly calm surface conditions on the east coast and noticeably smaller crowds at the more popular dive sites. With the wind coming from the west, the sea on that side of the island gets a little more ruffled, making it more popular with sailing enthusiasts. However, this is the last month of the sailing season before boat owners batten down the hatches for the coming monsoon season.