Saigon has two seasons: rainy and dry. I'd say hot and humid, but it's pretty much that way all year long! From May to October, afternoon thunderstorms are the norm with a deluge of rain coupled with thunder and lightning. We see some pretty spectacular storms from our apartment. Sometimes the cloud cover is so thick and dark we can't see across the river!
Fun fact: The lower end of the Saigon River is on the floodplain, and is therefore subject to tide change from the sea and the delta. It's neat to watch the river flow in both directions.