1993 Mitsubishi Galant Won't Start In The Rain

Engine Performance problem
1993 Mitsubishi Galant Front Wheel Drive Automatic 100k miles

I have a 1993 Mitsubishi Galant. For a few years now the car I've had a problem starting the car after a heavy rain, or several days out in the cold/damp. It will struggle but it will not turn over. I've had the car looked at by mechanics and they could see nothing wrong. The car will usually start again once it "thaws" out a bit and the temperature outside rises or the rain stops.