In August, the weather can be different, it's the beginning of the rainy season. However, last year, for example, it did not start, as well as the year before. There were some heavy showers, it still rains regularly at night, but during the day it's mostly dry and cloudless all the time. Air temperature 28-29, water temperature 29-30. The tides are almost imperceptible.
In September, the weather can be different, but mostly not bad. This is a transitional time between the rainy season and the high season. The rains, as a rule, at this time of year, if they do come, they are not very long (this has been the case in recent years, and last year there was no rain at all in September). For example, it may rain at night.