text: do thunderstorms weaken when they cross bodies of water?   there are a broad number of things which could happen when a thunderstorm crosses water. if the water is cool, yes it could weaken a thunderstorm.  but more often than not, if it reaches a body of warm water it will strengthen. if you've ever been in florida in the summer, you know about "pop-up" thunderstorms which form in the gulf and atlantic.  and if the conditions are right in tropical or semi-tropical waters, a thunderstorm could turn into a hurricane(which technically isn't a thunderstorm since it draws its energy from the heat of condensation and not from two layers of contrasting temperature air.