Andrea Cefarelli, executive director of donor recruitment with the New York Blood Center, said people donate less blood around this time of year.
The American Red Cross on Tuesday was pleading for blood donors to volunteer, with a serious blood shortage looming.
The string of snowstorms in recent weeks has forced the cancellation of many blood drives and deterred potential donors from visiting centers.
Blood Center Vice President Rob Purvis says supplies tend to dwindle when schools let out and people go on vacation.
Though hospital needs were met, and heroic donors found the NYBC facilities that were able to remain open, the unprecedented disruption depleted the blood supply to the point where a significant recovery effort is necessary.
The New York Blood Center is issuing an emergency appeal for donors.