What is causing the car to stall after the gas pedal is applied

It could be related to the rain and the ignition system. Also, you may have a bad fuel pump. What to do is start the car at night (in the dark) and look under the hood. See if any of the ignition components (plug wires, coil.) Are arcing. If you see anything sparking, it needs replaced and yes the rain is most likely causing it to do it. If there is nothing you see (with the engine running) check fuel pump pressure to confirm it is within the manufacturer's specs.