I visited Mt Rainer National Park in August 1980, with my family only a few months after the eruption. Even though I was only 13 at the time I clearly remember seeing the grey conical top of Mt St Helens on the horizon as well as everything being coated with several inches of volcanic ash. The other memorable thing was sunset at Mt Rainier which was amazingly red at the time.

A couple of years later, when I came back to visit in the US, I spoke with a local who was driving back to Seattle at the time of the big eruption, but was unaware the eruption was happening. He thought he was driving through a large thunderstorm, but then started to realize it wasn't rain falling but volcanic ash!

I still have an informational booklet on the Mt St Helens eruption that was published at the time.