Updated

An excessive heat watch is in effect for Saturday and Sunday as temperatures soar close to 100 in the metro area.

The record-setting heat wave begins Friday with highs predicted to reach 90, jumping another 10 degrees Saturday and Sunday under mostly sunny skies. The blistering temperatures come from an upper ridge of high atmospheric pressure.

"We've got high pressure over the area which brings us clear skies and a little bit of wind coming out of the east," said Amanda Bowen, a meteorologist with the National Weather Service in Portland. "When it's really warm on the eastern side of the Cascades, you get that warm air moving through the gorge before it comes into the area."

As winds east of the Cascades travel over the mountains into western areas of the state, those down-slope winds warm up the temperatures, she said.

Nighttime temperatures will bring some relief even though they'll remain relatively balmy: in the upper 60s on Saturday and lower 60s on Sunday.

The weekend temperatures should break records for the dates set at Portland International Airport: 91 on June 4 and 96 on June 5, both in 2003.

"We don't get 100 degrees quite this early very often," said meteorologist Paul Tolleson.

It's already been a warm year, Tollseson noted. "We've had 15 days in the 80s, which is a fair amount for this of year," he said.

People should drink fluids, avoid direct exposure to the sun and stay inside air-conditioned rooms if possible, the weather service advised. Check on elderly or frail people who might not be acclimated to the heat.

The hot spell will slack off slightly Monday with highs of 85 to 90 and then taper off Tuesday with a high of 75.

Multnomah County has planned the following cooling centers for the public:

* Multnomah County Walnut Park Building, 5325 N.E. MLK Jr. Blvd. in Portland

Sat. Open Saturday and Sunday from 4 to 8 p.m.

* Multnomah County East Building, 600 N.E. 8th St. in Gresham. Open Saturday and Sunday from 4 to 8 p.m.



Transportation to the cooling centers can be arranged by calling Ride Connection at 503-226-0700.

Clark County also directed residents to air conditioned buildings in Vancouver and cooling centers in Washougal:

* Marshall Community Center, 1009 E. McLoughlin Blvd., 5:30 a.m. to 9 p.m. Monday through Thursday; 5:30 a.m. to 8 p.m. Friday; and 7 a.m. to 7 p.m. Saturday.

* Firstenburg Community Center, 700 NE 136th Ave., 5:30 a.m. to 9 p.m. Monday through Thursday; 5:30 a.m. to 8 p.m. Friday; 8 a.m. to 7 p.m. Saturday; and noon to 6 p.m. Sunday.

* Vancouver Public Works' Water Resources Education Center, 4600 S.E. Columbia Way, 9 a.m. to 5 p.m. Monday through Friday, and noon through 5 p.m. Saturday.

Washougal cooling center locations and hours are listed on the Clark Regional Emergency Services Agency website.

-- Tony Hernandez

thernandez@oregonian.com

503-294-5928

@tonyhreports

An update to this post includes the locations for Multnomah County cooling centers and air conditioned buildings in Vancouver.

Jim Ryan of The Oregonian/OregonLive staff contributed to this report