I have been in contact with Tesla management to learn the best means of determining the status of Supercharger stations during emergencies such as Hurricane Irma.
Go to your car’s navigation system map and scroll into the particular Supercharger Station that you are interested in. Put your finger on the icon and the system will provide the status of how many stalls are available with a lag of 5 minutes. In the event of a power outage, the Supercharger station will display a “temporary closure” message to let you know the station is unavailable.