From July to October is the monsoon, when most of Thailand's annual rainfall is accumulated and flooding can ravage the country. The humidity averages just under 90%, with temperatures averaging around 29 degrees Celsius in a very wet and rainy Bangkok.
The monsoon finishes when the wind direction changes, bringing dry weather from the northeast. At best this season can be described as unpredictable and not the constant downpour of rain like you may expect. The middle months of this season may hold particularly heavy rains for the north of the country.