Strike? No close to no chance.
Weather, with the exception of the Far Rockaway pier this year there hasn't been many closings for weather. With the current warm winters, there hasn't been ice in the East River for several winters and both Pier 11 and Atlantic Basin are on the river or upper bay where there is rarely icing.
Get the NYC Ferry app for your phone, updated schedules and service advisories are posted there. With the coming schedule change at the end of March they are planning to add additional trips on the South Brooklyn route when a cruise ship is calling in Brooklyn.