The announcement is from Seattle Parks:

Many Seattle Parks and Recreation facilities and programs will be closed Thursday, Dec. 15, 2022 due to a Recreation Division in-service day.

These facilities and services are CLOSED:

All recreation programs
Community centers and teen life centers
Environmental learning centers
Indoor swimming pools
Green Lake Small Craft Center
Mount Baker Rowing and Sailing Center

These facilities are OPEN on regular schedules:

Parks
Amy Yee Tennis Center
Seattle Japanese Garden and Volunteer Park Conservatory
Boat ramps
Golf courses and ranges