From the Seattle Parks website:

Wading Pools are open on sunny days when the temperature is forecast to be 70 degrees or above.

Delridge Wading Pool:

June 27–August 21
Mon/Tue/Sat/Sun

12:00 pm—6:30 pm

MORE INFORMATION:
General Parks Information
206-684-4075

Wading Pool/Spraypark Hotline
206-684-7796

Wading Pool/Spraypark Questions
206-233-1500

Parks Website
www.seattle.gov/parks