Open House and Kite Festival, Blue Hill Weather Observatory, summit of Great Blue Hill. May 3, 10 a.m.–4 p.m. Annual event features information on the history of the oldest continuously operating weather observatory in the country. Activities include rooftop viewing, weather demonstrations, kite-making and kite-flying, easy activities for children, weather exhibits, lectures, displays, and self-guided tours of the weather observatory. To access the activities at the observatory, walk/hike the 1-mile route to the summit. Free parking at the Trailside Museum south parking lot near the Blue Hill Ski Area on Route 138 in Milton. Free, but nominal fee for some activities. 617-696-0562.