Yes, Monday is a holiday, at least for some. Memorial Day falls on Monday, May 31. PAT announces that —

The Port Authority of Allegheny County’s bus, T and incline service will operate on holiday schedules for
Memorial Day, this Monday, May 31.

Port Authority’s Customer Service phone line will hold holiday hours, 8 a.m. to 4:30 p.m., and the Downtown Service Center will be closed on Memorial Day. For more information, visit www.portauthority.org or contact a Customer Service representative at (412) 442-2000 or the TTY number, (412) 231-7007.