Visited at 6:30pm today (August 21, 2018). Posted hours (and Google) show the place as open until 7pm every day expect Sunday. The place is shut down. Does Mr. Wash routinely close early or is this unusual?

Only when they are expecting rain like today.

Right if there is rain they will close

We are usually open until 7pm weekdays. Yesterday we had severe weather conditions in Arlington and it was not safe for our employees to remain outside under these conditions. We closed for safety reasons. Please come back today the weather has much improved!