I realize that not everyone shares my affection for festivals of all kinds, but for those who do, summer in the Portland metro area offers up some good ones: Sherwood's Robin Hood Festival (so silly!), the Crawfish Festival in Tualatin (so delicious!), and this weekend's Festival of Balloons in Tigard (so balloony!).
At the risk of sounding far older than I actually am, hot air balloons are neat. Or, as the creator of the above video put it, "Everyone seems to like balloons. The people were very nice and it was a great sight to see." Aaaand you can see for yourself this weekend, Thursday-Sunday at Tigard's Cook Park. The balloon launches are super early, but there's a carnival and beer garden and other stuff too.
The fest also offers the fun-sounding Twilight Run, a 5k through Cook Park, which every year I consider doing and then don't. Cook Park is great—it's part of a surprisingly large interconnected park system that joins Cook, Durham, and Tualatin parks via pedestrian and bike trails, and includes wetland areas and access to the Tualatin River. It's a pretty stellar little park system, especially if you like looking at birds and things. (Apparently I am 60 now.) The run is $30, but proceeds directly support the Tigard-Tualatin school district—more info here.