In addition to the hot afternoons, little relief from the heat is expected overnight. With little to no cooling influence from the ocean and a somewhat humid air mass in place, nights will remain quite uncomfortable away from the coast.
An excessive heat warning means that a prolonged period of dangerously hot temperatures will occur. The combination of hot temperatures and high humidity will combine to create a dangerous situation in which heat illnesses are likely. Drink plenty of fluids, stay in an air conditioned room, stay out of the sun, and check up on relatives and neighbors.
For the most up to date weather information from the NWS please visit http://www.weather.gov/portland. This page brings up all advisories, watches, and warnings for the southwest Washington area.