The US Postal Service is taking the rare step of cancelling mail delivery for portions of the Midwest, including most of Michigan, due to the subzero temperatures.

The USPS says that for Michigan ZIP codes that begin with 486 to 499 and Detroit codes 480 to 485, no mail will be delivered Wednesday, January 30. That includes Battle Creek, Kalamazoo, and most of their surrounding areas.

The postal service says the cancellation is out of concerns for safety for their employees.

The USPS is well known for their slogan "Neither snow nor rain nor heat nor gloom of night....", but according to a report by their historian in 1999, that's not actually an official motto. The full quote reads as thus:

Neither snow nor rain nor heat nor gloom of night stays these couriers from the swift completion of their appointed rounds.

This phrase is actually chiseled above the entrance to a Post Office in New York City, and is a quote from The Persian Wars by Herodotus; in context, the Greek historian recounts the great drive with which Persian couriers did their jobs in the Greco-Persian Wars of 500-449 B.C.

The USPS in their historical analysis notes that the belief this is an official motto is "a tribute to America's postal workers."