If I were to dry the bike after each bout of humidity, I wouldn't be using it throughout Winter or 1/3 of the time in Summer.

Basically, the only really problematic areas are:
- the saddle: if you have a leather saddle, use fenders (to protect the underside) and protect it from the rain when you stop;
- the drivetrain: the chain needs re-lubrication more often and cleaning at shorter intervals. The best lubricant depends on weather and the roads you face: "dry" lubricants keep the drivetrain clean but need to be reapplied after each drop of water (so it seems), whereas wet, greasy lubricants seem effective for ever... but are also wonderfully effective to catch all the grit around.

Finally, I have full fenders and mudflaps, which not only keep the bike relatively clean, but also protect the chain and bottom bracket from roadside projections. Bonus: they also keep the rider -- me -- clean.

Regards,