Gwarren, I had that happen to me once in a bad rainstorm and I believe the rain water got up on the bottom of the separator bowl where the Water In Fuel sensor is and made it come on. It still worried me to death but I resisted the urge to pull over and the light went out. Later I checked the bowl and drained some fuel into a glass jar and nothing. It has never happened again and I have never found water in the bowl. I wouldn't worry about it and write it off to the rain storm.
"Gunner" USN Retired, Airdale
2004 Monaco Signature 44' Conquest. Detroit 60