I have it on good authority that all US markets will be shut down as a result of hurricane Sandy. This includes electronic trading which is a new addition – earlier you may have heard human trading was to be shut down. Exchanges affected according to sources are NASDAQ, BATS Direct Edge, NYSE CME and CBOE.
This will definitely happen unless Mary Shapiro, chairman of the SEC overrules the decision.
Moreover a shutdown like this as a result of weather is very rare.
I wish you all a safe and secure week.

Update: All cash markets and options markets will be closed on Monday and Tuesday.