"""Glass is visible on roads by its shiny splinters and shards as well as not being the same color as the road. When wet from rain, these characteristics vanish and leave glass looking like any bit of gravel.""

""When wet, glass can stick to the tire even in the flat orientation and thereby get a second chance when it comes around again""

""To make things worse, glass cuts far more easily when wet as those who have cut rubber tubing in chemistry class may remember. A wet razor blade cuts latex rubber tubing in a single slice while a dry blade only makes a nick"""

I also think that debris from the road has a much greater opportunity to stick to the surface of the tire when wet providing more opportunity for punctures.

also small and large depressions collect sharp debris and glass, they become puddles /tire booby traps

I moved to Manhattan 6 months ago and during the past 6 months have ridden my bike to work every day. The amount of glass my tires has picked up definitely gets my attention... the glass is mainly due to car break-ins and surprisingly, is almost everywhere. That's true about the increase in glass punctures when the roads are wet- something to think about before hitting the road in wet weather.