If you have a distributor cap, do check it. It's a cheap fix to replace it anyway.
I STILL believe that the ignition coil is your problem, based on my experiences with hard starting in moist weather.
But start with the cap, and then take a look at that coil...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car