Unfortunately, like Michael said, it is a fact of life. I live in FL and down here we always have high humidity. When I travel around the state on business, I am frequently up to photograph sunrises. The problem is that I like my hotel room very cool at night. Since, unless it is winter in North FL, the outside temperature in the morning is usually in the high 60's low 70's with high humidity. Obviously coming out of a very cool (usually low 60's) room into the humidity spells fog on the lens. Since I don't want to leave my equipment in my vehicle, I started putting my camera backpack in the closet of the hotel room on the highest shelf (heat rises) with the door closed. I wrap the backpack in an extra blanket or towels if no blankets are available. After I am dressed and ready to walk out the door, I grab the bag. This has seemed to help prevent the fogging in all for the highest humidity days.

I realize this won't exactly help in your situation as you aren't coming from a hotel room at the time, but there may be a a time you could use this tip.

Good luck
Terry