Fox News Weather Center

90-degree heat to build across northwestern US this week

Dangerous heat will surge northward and send temperatures soaring across the northwestern United States this week.

The core of the heat has remained bottled up over the southwestern U.S. for much of the month, but that will all change during the final week of July.

"For the most part, the heat has stayed away from the Pacific Northwest since the second week of June," according to AccuWeather Meteorologist Michael Doll. "Temperatures have averaged near or slightly below normal since then."

An expanding area of high pressure will put an end to the seasonable trend during the final week of July.

The heat will reach its peak during the middle and later part of the week, when high temperatures will soar to 10-15 degrees Fahrenheit above average in places like Seattle and Portland, Oregon.

Highs in the upper 80s and low to mid-90s F will be common across Washington and Oregon by week's end. The century mark may be surpassed in some spots.

Should Portland, Oregon, reach 90 later this week, it would be the first time since June 6, Doll stated.

Even areas farther south that are used to 90-degree heat in the summer will experience a slight rise in temperatures this week. Sacramento and Fresno, California, are both forecast to endure multiple days in the low to mid-100s.

Coastal areas under the influence of the cool waters of the Pacific will offer residents and visitors a refreshing retreat from the heat.

Northwest residents who may not be accustomed to the heat due to the rather seasonable conditions so far this summer should take necessary precautions this week.

Any outdoor activities should be confined to the early morning or evening hours. Those who must be outside during the heat of the day should wear light-colored and loose-fitted clothing, take frequent breaks in the shade and drink plenty of water.

Local malls, libraries and senior centers can provide relief for those without air conditioning.

Remember to never leave a child or pet unattended in a vehicle.

While the building heat will provide excellent opportunities to head to the local lake or pool, the hot and dry conditions will only worsen the wildfire situation across the West.

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The Sand Fire near Los Angeles continues to blaze a path of destruction after it exploded in size on Saturday.

As heat expands this week, new wildfires could ignite farther north.

"Due to the lack of heat [across the Pacific Northwest], very few large wildfires have occurred across Oregon and Washington," Doll explained. "However, with the higher temperatures on the way later this week, the fire danger will rise."

Temperatures are forecast to fall back to more seasonable levels early next week.