If you can thoroughly dry out the plug wires, coil and cap (inside and outside) with a clean rag; it will often be enough to get the engine going. Removing the plug wires from each plug one by one, and drying the plug porcelain and the wire boot is also helpful, along with applying silicone grease to the inside of the boot and the cap and coil terminals; so that it seals on the wires and the plug insulator. Spraying the wires and cap with WD-40 will also drive the moisture out of the igntion system.
If these measures do not help; it sometimes is necessary to reduce the plug gap from the standard .060" down to .045."
I hope this helps!!!