Squarespace founder Anthony posted an update on downtime due to sandy in their status blog. Its amazing what they were doing to keep their customers online.
We had an initial warning that 10:45am was going to be the clean shutdown time. To determine how much time we have remaining, engineers are taking readings at particular time intervals to attempt to determine how quickly we are depleting. The tank readings are behaving somewhat erratically, as there is another mechanism replenishing it from a separate fuel header. Some of our recent readings seem more optimistic, but it is impossible to predict how much fuel remains in this header at this time. As of this writing, we have at least 45 minutes left.
Bridges to the island are open right now, and we currently have a fuel truck en route. We have approval from the building to manually carry fuel up and we have a number of our team on-site to offer manual help as needed.
I recommend to read this status update post.