I'm guessing spark voltage is arcing to the engine metal rather that to the spark plug because of worn out spark plug wire insulation. You may be able to observe this when the engine is running at night in a dark location when it is wet outside by opening the hood and observing for arcs jumping out from the spark plug wires. The distributor cap could also be cracked which can also short the voltage to ground. So my first suggestion is to replace the spark plug wires and look carefully at the distributor cap for any signs of a crack. Then report back.
happened to my sisters civic quite a few times, i think it was the alternator or some other electical part got water in it and just wouldnt work :/ sorry i cant be more help but it was about 3 years ago i fixed it and i cant remember what i replaced
After it rains open your hood and look for water check around the battery, the starter, the alternator, check for loose wires, replace your dizzy and get new spark plugs and wires that should solve your issue
edit. Just saw you found the problem it's still reccomended to change your wires and sparkplugs