According to the Bethel Woods Center, Stevie's show Saturday night is still on...
Obviously this could change as Irene moves closer to the NY area... Keep checking their facebook page for updates.
"The Stevie Nicks concert on Saturday, Aug 27 is on as scheduled with an 8pm show time. We are carefully monitoring the weather conditions with local and national agencies and will update as needed. Currently the storm is expected to hit our area around 8am on Sunday morning."
Per: Bethel Woods Center on Facebook