Don't let the United States Postal Service creed fool you — there are two occasions that cause disruptions in mail services: legitimately life-threatening inclement weather and, apparently, papal visits.

Philadelphia residents in eight different ZIP codes won't be getting any mail when Pope Francis pays a visit to the city later this month, on Sept. 26-27. The affected areas all fall inside the security perimeter that will be overseen by the U.S. Secret Service.

Four different post offices are affected in all, according to Philly.com: the Philadelphia Main Office (ZIP codes 19102, 19103 and 19104); the William Penn Delivery Annex (19106 and 19107); Fairmount Station (19130); and Spring Garden Station (19122 and 19123). Mail delivery in those areas will conclude on Friday, Sept. 25 at 1 p.m. and resume on Monday, Sept. 28.

Blue mail collection boxes will also be removed from those ZIP codes, according to Postal Service spokesman Ray Daiutolo, Jr. "We won't be able to get in there with vehicles or people on Saturday," he said.

The service disruption will also affect the business hours of post offices all throughout Philadelphia. Individual locations will operate from 9 a.m. to noon on Friday, Sept. 25 for non-card services in Aramingo, Germantown, Nicetown, Northeast Philadelphia, University City, South Philadelphia and Upper Darby.

The Pope's imminent arrival has been no small source of consternation as city officials prepare for a record turnout. "This will be the largest event in the City of Philadelphia in modern history," Mayor Michael Nutter said during a June press conference that was held to address public transportation concerns related to the visit.

Visitors will be ferried around by a mixture of public transit and charter buses, but due to security concerns and unmanageable foot traffic it's likely that most will be dropped off a considerable distance from the front steps of the Philadelphia Art Museum, where the Pope will celebrate a Mass. Many roads and highways are expected to be closed, and heavy traffic is expected for those that remain open.

Nutter warned Philadelphia resident in June that they should "be prepared to walk a few miles or more" while the Pope is in town. "Private vehicles will really not be a viable option," he said.

It's hard to say just how many attendees the Pope's arrival will bring, but a 1979 visit to Philly from Pope John Paul II drew an estimated 1.2 million to 2 million. Nutter warned residents to expect a similar turnout this month.