Some 24 million people in six states are under heat alerts as the Pacific Northwest braces for a potentially record-breaking heat wave this weekend.

       On Saturday, highs are expected to hit triple-digits in Portland, Oregon -- up to 107 degrees. The high for Sunday is expected to reach 111. The hottest temperature on record in Portland is 107 degrees.

       In Seattle, highs are expected to reach 99 degrees Saturday and soar to 103 degrees on Sunday and then 108 degrees on Monday. The all-time record in Seattle is 103 degrees.

       Typically this time of year, Washington and Oregon see average highs in the 70s.

       Dozens of daily record-high temperatures are expected to be broken from Washington to California. Other affected cities include Medford, Oregon, and Redding in Northern California. Parts of Southern California, Nevada, Idaho and Montana also are under an excessive heat watch or warning this weekend.

       ABC News

       A historic heat wave is expected to bring scorching temperatures to the Pacific Northwest.

       There's also an elevated risk of wildfires in the Pacific Northwest.

       MORE: Pacific Northwest braces for historic heat wave, and experts say climate change could be to blame

       The dangerous heat conditions are expected to continue into early next week. The prolonged period of heat in the Pacific Northwest is of concern for the typically mild region, especially as many residents don't have air conditioning.

       "This event is blowing our minds," Treena Jensen, lead forecaster for the National Weather Service in Portland, told "Good Morning America." "We have never seen computer models show temperatures this hot for this area. It's astounding."

       Ruth Fremson/The New York Times via Redux

       People take in the evening at Alki Beach in Seattle, June 24, 2021. An intense heat wave is set to pummel the Pacific Northwest, potentially setting records in Seattle, Portland and the interior.

       Officials in Multnomah County, which includes Portland, have set up cooling centers in preparation for the unprecedented heat. Dozens of locations in the Seattle region also are extending their hours to help provide relief.

       "This is truly dangerous heat," Multnomah County Health Officer Dr. Jennifer Vines told "Good Morning America." "Our evening lows are around our average yearly highs for this time of year."

       MORE: Heat wave safety: What to know about heat stroke vs. heat exhaustion

       The elderly and young children are especially vulnerable, experts said. People are advised to stay indoors when possible and stay hydrated.

       "Really be on the lookout for excess thirst, where you feel like you're needing to drink a lot, that you're feeling a little bit weak or dizzy," Dr. Daniel Henning of UW Medicine told ABC News Seattle affiliate KOMO. "If it gets more extreme, you might see people acting more confused."

       ABC News' Brittany Borer and Hope Osemwenkhae contributed to this report.