windy.com can be very handy for planning imho - the weather models aren't great at predicting fog but call up a forecast on windy then click the webcams in the vicinity button to see live & recent webcam images to see what it really looks like or looked like >
Spent an interesting night in Galicia fog a few weeks back - it is almost as good as a haar. Thankfully, the boat had radar and we were close enough to shore for the Vessel Finder app to work. That big ship underway, but not making way, had me puzzled for an hour or so.