You can head to the beach but shade, cool drinks and better yet air conditioning will help of course.
The National Weather Service has a heat advisory in effect until 10 PM Monday night Aug. 16.

Here are some other tips you can try:
Close windows and blinds during the heat of the day.
Unplug unnecessary appliances and electronic equipment – coffee machines, microwaves, printers, etc.
Reduce lighting to minimal levels.
Investigate personal and space cooling with small room fans and ice packs.
Set your printers to power saver mode when they are not in use.
Set your computer screens to power saver mode when they are not in use.
Turn off all unnecessary lights.
Consume fresh, cold meals or cook during cooler hours.
For residents that don't want to escape the sun by hiding inside with an array of fans, ice packs and popsicles,
Seattle Parks and Recreation offers its outdoor pools, water features and beaches.

The wading pool for toddlers in Lincoln Park is open daily in the upper park or you can head over to E.C. Hughes at 2805 SW Holden St., noon to 7 p.m. Wed, Thu, Fri through Aug. 20. for their 'Three Day' wading pool.

Other options locally include heading to the Southwest Community Pool 2801 SW Thistle St or to the Admiral Theater for their air conditioning or Fresh Bistro 4725 42nd Ave SW, West 5 restaurant in the junction or the Porterhouse Restaurant 2329 California Ave SW in the Admiral District, or Barnes and Noble at Westwood Village is always well cooled.

You might even take a few minutes to drop by the Duwamish Longhouse and Cultural Center 4705 W Marginal Way Southwest to learn about the first people to live in this area...and cool off.

King County has these helpful suggestions too to beat the heat:

http://www.kingcounty.gov/healthservices/health/beattheheat.aspx