The windshield gasket needs to be replaced (mine began leaking during an almost monsoon-like storm in Houston). When the windshield is off look for rust in the channel where the gasket fits into. Remove any rust and repaint. Fast Lane on this site sells the gasket and have a shop R&R for you since they have the tools/experience to do the job right and minimize the chance of breaking your windshield.
America: Land of the Free!
1977 300D: 300,000+ miles
American Honda: Factory Trained Technician & Honor Grad.
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.