Free day in state parks: In honor of National Public Lands Day. A Discover Pass still required to access lands managed by the Washington State Department of Natural Resources and the Washington Department of Fish and Wildlife.
Crayfish boil: 4 p.m. UW Associate Professor Julian Olden will host a crayfish boil at Pine Lake Park.
Thriller flash mob rehearsal: 5-6 p.m. at Blakely Hall in the Issaquah Highlands, 2550 NE Park Drive. Flash Mob performs twice at the 13th Annual Green Halloween Festival on Oct. 26.
Urban Village Development Commission: 7 p.m. in Issaquah City Hall council chambers, 135 E. Sunset Way.
Youth Cyber-Safety: 7-9 p.m. Attorney Charles Leitch will hold a free presentation for parents at Alcott Elementary, 4213 228th Ave. NE. The talk will cover how to talk to children about safe use of social media.