In a conference call with the press, the Federal Communications Commission (FCC) Chairman Julius Genachowski said that across a 10-state area between Virginia and Massachusetts, 25% of all cellular sites are non-operational as a result of tropical storm Sandy. This was as of 10 a.m. EST today.
The outages that are occurring in a combined 158 counties within the 10-state stretch are apparently just the tip of the iceberg, however. Genachowski predicts "communications outages could get worse before they get better, particularly for mobile networks," as the storm continues to move west toward Michigan.
It was also noted that numerous cell sites are running on backup power supply, but those could very easily go down as well if workers are unable to replace batteries or re-fuel generators in time.
In terms of how many individuals in the U.S. are without cell service, the FCC couldn't confirm that figure, since it's possible that some users in storm struck areas are still managing to pick up signals from nearby towers.