This is how you know it’s really cold: The polar vortex is putting mail delivery on hold in ten states. Some retail post offices will be open, but couriers won’t be delivering any mail in the affected states. The USPS announced that no mail will be delivered in parts of Michigan, Iowa, Minnesota, North and South Dakota, Wisconsin, Illinois, Indiana, Ohio, and Pennsylvania. Some retail offices of the postal service will be open, but couriers won’t be delivering any mail to those areas.

It’s not just schools that are closed. The bitter cold has businesses, local governments, and even Amtrak to close their doors for the day. The Post Office is canceling mail service because it’s just too cold. The Illinois State Police are telling people not to travel unless they absolutely have to.