2002 Ford Escape running rough when it rains?

My 2002 Ford Escape (162,000 miles) was running terribly, and after taking it for 2 diagnostics, my dad changed all 3 catalytic converters, along with the O2 sensors about a month ago. It ran great after that. Went to leave yesterday, and it sounded terrible again-it had been raining profusely and I park under a carport-the concrete was wet, but dry under my car. We started it today, and it sounded fine. Could this be a very weird evaporation issue, where the spark plugs (or something) are getting wet? I like my car, help! Thanks