The Washington Park Zoo announced it will open for an extended hour later on Saturdays and Sundays starting Saturday May 28 until September 4.
Monday through Friday hours will remain 10:00 a.m until 4:00 p.m with the last admission being sold at 3:00 p.m
Extended summer hours are Saturday and Sunday 10:00 a.m. until 5:00 p.m with the last admission being sold at 4:00 p.m.
Check out their website for more information.