It depends on what is scheduled at the time when the weather related event takes place, earthworks will be most impacted in the event of snow or ice.
Rain should normally not make as much of an impact unless it is sustained, tends to be more of a productivity issue. It will definitely slow things down a bit unless flooding has occurred in the vicinity. From contracts I've been involved in it is unusual for more than a couple of weeks to be lost over the course of long term construction contracts (remember good weather can accelerate delivery). Anybody have access to weather station data for the area over the last few months?
All contracts I've ever come across will have 'average' weather related events built into the schedule so, unless its 'extraordinary' (i.e. 1 in 50 events) it should not impact the works schedule.
I'd wager that the delays are probably not weather related, or at least certainly not the overriding issue at play here.