Very interesting thread. Here in RI, they are classifying this as a blizzard. As our local meteorologist pointed out, a blizzard is defined by the NWS as having the following :
1. When visibility is cut to a 1/4 mile or less due to 'white out conditions'
2. Sustained winds of 35 miles an hour or greater for at least three consecutive hours
3. There is snow - though it DOES NOT MATTER HOW MUCH OR HOW LITTLE snow actually accumulates. (She pointed out this is where most people are mistaken, thinking you have to have at least a foot of snow).
So if these three conditions are happening in NYC today/tonight, the NWS says you are indeed having a blizzard.
Locally, I know that if a touring B'way production is in town, the show is never ever cancelled unless the Governor declares a 'state of emergency'; in which no one is to travel on streets unless you're an 'essential worker' going to your job. Only then can the theater cancel, and have limited financial liability from cancelling. (they will either refund tickets or offer comparable tickets to another performance on the schedule, or a show which they have coming in - most thicket holders will take the comparable tickets, from what I've been told). As for the performers / production, under a state of emergency, the theater is not financially obligated to pay for that performance. However, if there is room in their schedule - they will usually add a 'matinee' performance on one of the remaining days and they do get their pay and ticket holders have that option. (This is what they have done MOST of the time). This is why the theaters never ever cancel performances on their own - unless the Guv declared the state under emergency.
The same holds true for other major touring events - concerts, skating events, etc. The show will go on, unless a SOE.
As for the regional theaters - same rules apply. The show will go on unless the Guv declares a state of emergency. Those theaters almost always add on a performance - either during the run or at the very end of the run, as these are repertory theaters, and don't host travelling shows.
I do know all this from a friend of mine who had started out in theater management for a regional theater back in the 90s, and currently holds a similar position in the theater which hosts the national tours. Of course, I'm not saying these rules apply for every regional theater or performing arts center across the country, but this is what follows in my corner of the world.