Headlight fuse blows when engine get hot

Had an issue this past week at Myrtle Beach. Two seperate times in heavy, stop and roll traffic, because the MB DOT decided to close north bound ocean blvd...my engine heat was really high. No thermometer, but definately, 'seat of the pants' testing. Anyhow, both times my light fuse popped (no lights at all...headlights, taillights, brakelights, etc). I at first thought i had a short or something, but i have never had this happen before. After i changed the first fuse, i was ok for 50-60 miles, until i got into heavy traffic again. Is this just a coincidence. I checked the wiring once i got back home, and didnt find anyting unusual.
Has anyone seen similar issues or have a clue as to why a hot engine will pop a fuse?

New on on me Hardy...must be a thermal circuit breaker or did the fuse element actually melt?