That includes the city of Philadelphia, along with Chester Co., Delaware Co., Bucks Co., and Montgomery Co.
The USPS says it will attempt to collect items in post office boxes by noon.
Retail services in Philadelphia are limited, and customers are asked to call ahead for hours.
All retail services will close at 4:30 p.m.
The USPS also asks customers to clear walkways and areas around mailboxes of snow and ice. Letter carriers are instructed to take precautions and to hold mail to addresses where ice and snow are not cleared.
