Do it. Really. Get outside. Nothing can improve a baby’s mood (and yours) like getting outside. Just the other day my teething and fussy 5-month-old nephew spent a contented 30 minutes outside listening to the rain dropping on our camellia and winding dried maple leaves around his finger.
Hard to get out on your own? Consider finding a local hike or outing through Hike It Baby, a growing organization that helps outdoors-oriented parents meet up. Another option is to search Meetup.com for a number of mom and dad groups that plan hikes and outings all over the greater Seattle area.
Other strategies to do on your own and with others: Find a good roster of any-season parks and rotate your visits. The minute our daughter could hold up her head we were swinging and sliding with her. Get a comfortable carrier so you can carry your child close as an alternative to the stroller.
Don't forget to blow their minds with beauty. Make a trip to one of the area's amazing local gardens to get some calming endorphins and make your baby happy. In the Seattle area, I recommend the Volunteer Park Conservatory, Seattle Japanese Garden, Kubota Garden, Bellevue Botanical Garden, and (a bit farther out) the Bloedel Reserve on Bainbridge Island. In the South Sound, wander along Tacoma's Ruston Way or explore the beach at Titlow Park. You can also wander around for free in one of the beautiful nurseries in the area, such as Swansons, Sky, Watson's or Molbak’s.