Hermiston Police Department issued the following announcement on May 26.
The annual Hermiston High School Senior Parade will be happening tomorrow evening (May 27th) at 7:00pm. There will be a brief disruption (due to some street closures) for traffic utilizing roads around the high school at that time. These delays generally don't last more than 15-20 minutes for this event. Attached is a map showing the route if anyone wants to join in at congratulating our graduating seniors.
Original source can be found here.
Source: Hermiston Police Department