I'm not a lawyer so I can't argue as such. But it's pretty clear that a major snowstorm has knock on effects and many days of delays and cancellations which is not unique to EWR but happens at airports all over the world. Any cancellation due to weather will not be met with EC261/2004 payout as I believe a) it meets the criteria of exceptional circumstance; and 2) it's outside of UA's control. They do not control EWR. Now, again, if there's a reasonable delay/cancellation within UA's control then obviously the rule would apply. And if someone wants to take UA to court in the EU over a delay/cancellation 2 days after a major snowstorm I say go for it but you're likely wasting your money. I don't think the European courts have said what constitutes a "normal return to service" from such an exceptional event.

As of this writing EWR has a 3 hour ground delay posted with an arrival rate of 20 per hour. That's incredibly low given there's no weather in EWR right now (not snowing, no wind, it's just cloudy and cold).

-RM