any old car is prone to it really, coil, leads, distrib all have a limited life span and as they get old the rubber and plastic perish and thats when you get damp issues.
i used to keep a huge can of wd40 in my old car as every other morning id have to give the engine a spray in winter to get it started.
not sure about your engine type, but i used to pop off all the leads at each end and give them a squirt of wd40 to ensure all the contacts were free of water. and also give the coil a sray too. dont miss out the lead between the coil and the distrib. if the engine then runs smoothly then its probably time you got a new set of leads.
if after all that it doesnt work then you will need to look into other issues like the distrib and coil themselves, failing that, maybe the throttle body as mentioned above.
but if this has only just started since the wet weather then damp wld be the likely suspect.