Moisture isn't what kills the components inside your PC motherboard, psu etc....it's dust + moisture that kills them...in summer humidity is very low and air is dry which carries dust that gets deposited over the months inside your PC....rainy season usually follows summer when humidity becomes very high and the moisture in the flowing air through your PC gets absorbed by the dry dust deposited over the summer and that can cause a short in your electronic components killing them.
Moisture on it's own will take many years to kill your components via corrosion, ie especially if you have kept your PC etc shut down (not in use) for extended period of time.
Clean your PC at least once a year just before rainy season starts and of course make sure you don't zap your motherboard, PSU-board with static electricity from your body. Religiously touch the metallic back of your PC cabinet (with power cable still connected to provide ground), before touching the inside electronics..