It's march now and since December I've had a handful of times where my car starts really hard the day after we have a day with lots of moisture of some kind (rain, wet sloppy snow etc.) I park in a dry heated garage so after it sits for the night it doesn't want to fire right up. It seems to be getting worse and my mechanic checked the plugs and coils and said they were fine. It's got him scratching his head. Once the car starts, it's completely fine until the next wet day.
Ideally the car should be tested during the actual hard start period, often checking after the problem has cleared especially when the problem is only experienced at certain times can be rather frustrating for the mechanic, I would be inclined to be looking further into the ignition system as this can be weather affected with moisture in electrical harness connections I would be looking here.