I lived in Cairns for a couple of years and it's tropical, stinkin' humid. Like, so humid it gets into your bones. It was like being wrapped in a hot wet blanket constantly. You could chug a litre of water in one gulp (I'm not exaggerating; I used to drink out of a litre measuring jug so I wouldn't have to keep filling up my glass) and being in the shower was not much different from being out of the shower. You'd work up a sweat brushing your teeth. Yet the brothers HAD to go witnessing in the tropical heat in ties and slacks. They wilted like sick flowers by 10-10:30 and that was the end of it for most of them. The sisters were better off because we could wear skirts, sandals and sleevless tops, and we always carried umbrellas.
We never went out door-to-door during the monsoon though. We did calls then, if anything.