When I searched this issue the closest solution I found to the one I came up with was to remove the bulb socket and blow warm air into the headlight with a hair dryer. My solution was to simply secure an electric heating pad against the light and in about an hour (---or until the heating pad automatically cycled off???) the lens was perfectly clear. I'm sure the problem will re-appear when conditions warrant - but drying the lens up in this manner was an easy fix. Now, if I can just figure out where the moisture is getting in-------

 

As suspected, the moisture did re-appear - but it is definitely a humidity problem as the car was not in in a rainstorm or car wash yesterday. I re-applied the heating pad and it disappeared again. Maybe Volvos suffer from sinus problems too!