Moist air is fine, wet is not. It even helps to cut down on the static risk. And you should always let it sit for a bit after cleaning before turning it on in case there was moisture build up.

The biggest risk is to reach into the guts and zap a component, that's a much higher chance of incidence than any effect from the air itself, after all, the fan also sucks air through all day long and usually is not grounded.

Make sure you always reach for the frame first before touching anything else in the guts of a computer.