1. When you say that the car will not start in wet weather,,do you mean that the car has been sitting all night,,,or it has been sitting all day,,and this is the first time that you try and start it ?
2. Or do you mean that you were just driving the car,,,in the rain,,,or on wet roads,,and you shut the car off,,,and now it wont start ?
If the answer is yes for number 1. then the problem may be in a faulty sensor,,are the hood and cowl weather strips intact,,water may be leaking past a leaking seal and causing a wire to short to ground.
If the answer is yes for number 2. then a wire or harness connector in the engine compartment or somewhere under the car that is exposed to the weather is getting wet and is causing a electrical short to ground,,look for loose connectors,,dirty or corroded connections,,cracked or damaged wiring.
Some connectors require weather tight connections to keep out water,,some connectors require water resistant grease to keep out water,,depending on region and application.