Dear Tom,
When I was in Miami, my windshield was slimy with salt water from the frequent showers. If much of our precipitation stems from Gulf of Mexico moisture, why isn’t it salty?
— Jim Sobun
Dear Jim,
The salty slime that was on your windshield in Miami was not from the rain, but from ocean spray.
The salty spray carried by onshore winds affects the environment by damaging vegetation and rusting metal. Southeast Florida residents reported widespread rusting in the wake of Hurricane Andrew in 1992 when the storm’s 165 mph peak winds blew massive amounts of salt spray inland. A hurricane’s storm surge will also carry salt water inland, wreaking havoc on vegetation.
However, rainfall is fresh water, as the salt in the seawater is left behind as the ocean water evaporates into the atmosphere, just as salt is left behind when a pot of salt water is boiled dry on a stove.
