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A pyrocumulus cloud caused by the Bootleg Fire, 27 miles northeast of Klamath Falls, drifting into the air north of the Bootleg Fire forward operating base in Bly, Oregon on July 15. Photo: PAYTON BRUNI / Getty Images

A total of 70 large wildfires are burning across the U.S., according to the National Interagency Fire Center, and this number is likely to grow as yet another powerful heat dome is set to build across the West, sending temperatures skyrocketing.

Why it matters: States across the northern Rockies and parts of the Pacific Northwest are set to see another searing heat wave from Saturday through at least Wednesday, with temperatures hitting 20 to 30 degrees Fahrenheit above average. This could significantly exacerbate the wildfires that are already ravaging the territory.

  • Forecasters with the National Weather Service warn of the potential for thunderstorms to form that could deliver little rain but dry lightning strikes that may spark new blazes.
  • These same areas that will see the extreme heat starting this weekend — including Montana, Idaho and Wyoming — are affected by wildfire smoke wafting in from fires in California, Oregon and Washington.

Driving the news: The Bootleg Fire, the largest wildfire currently burning in the U.S., has demolished more than 230,000 acres in Oregon and remains only 7% contained, per the Inciweb.

  • Some communities surrounding the blaze are still being evacuated, officials said on the Bootleg Fire Facebook page.
  • The NIFC, which coordinates federal firefighting agencies, on Thursday elevated its national alert level from 4 to 5, the highest on its scale and the earliest such designation in 10 years.

The big picture: The extreme drought and heat waves, which researchers say have been aggravated by human-caused climate change, are the main reason why this year's wildfire season ramped up so early.

What to watch: High temperatures on Monday in northeastern Montana could top 108 degrees Fahrenheit, with the heat stretching through midweek, according to the National Weather Service.

  • Computer models show that yet another heat dome is building across the West, this time moving north and parking itself over the northern Rockies, drawing warm air northward and locking it in place for an extended period.
  • This heat comes on top of an already hot streak, in the middle of a record drought. Boise, Idaho has reached or exceeded 95°F for a record-setting 20 straight days. The heat plus drought is leading to some of the driest vegetation for so early in the fire season -- a clear warning sign of the potential for additional large blazes.
  • The heat may be most extreme in portions of southern Canada, including British Columbia, Alberta, Manitoba and Saskatchewan, where above average temperatures may stretch for longer than seven days. Numerous fires are burning in Canada, sending smoke eastward all the way to mainland Europe.
  • The extreme heat will contribute to the potential for unusual wildfire behavior, including the development of towering clouds of ash and water vapor, known as pyro-cumulonimbus clouds, or pyroCb. These can spark new blazes via lightning, and alter winds in ways that make firefighting efforts extremely difficult.
  • This most recently happened Thursday with the Bootleg Fire.
A tweet previously embedded here has been deleted or was tweeted from an account that has been suspended or deleted.
  • While not in the area of intense heat, a fire weather watch is in effect for Sunday to Monday in the San Francisco Bay area due to an expected outbreak of thunderstorms that could touch off some fires. These storms are not expected to bring drought relief, however.
  • More storms could form further north, in Oregon and Washington, potentially causing additional fires there too.

Go deeper:

Go deeper

Sequoia National Park Forest wraps trees in foil as wildfires approach

View of giant sequoias in Sequoia National Park. Photo: Anne Loustaunou/Corbis via Getty Images

Sequoia National Park Forest officials have wrapped giant sequoia tree trunks in aluminum foil insulation due to two uncontained California wildfires that are projected to spread toward the park.

Why it matters: Giant sequoias are unaffected by most wildfires, but among the trees currently under threat is The General Sherman Tree, which is approximately 2,300 to 2,700 years old.

UN warns of "catastrophic" climate change failure without more emissions cuts

UN Secretary-General António Guterres at a news conference. Photo: Fabrice Coffrini/AFP

A United Nations report released Friday warned that the planet will likely warm by more than 2.7 degrees Celsius by the end of the century unless governments take extra steps to curb greenhouse gas emissions.

Why it matters: The report, released just months ahead of November's UN Climate Summit, highlights the growing pressure on global leaders to crack down on emissions to avert the worst effects of climate change.

Updated 2 hours ago - Politics & Policy

Pentagon approves request for 100 National Guard troops for "Justice for J6" rally

Security fencing has been reinstalled around the Capitol. Photo: Drew Angerer/Getty Images

Defense Secretary Lloyd Austin has approved a request from Capitol Police to provide 100 D.C. National Guard troops in case law enforcement requires additional support at Saturday's "Justice for J6" rally at the Capitol.

Why it matters: Security preparations have ramped up ahead of the pro-Trump demonstration, where hundreds of protesters sympathetic to the Jan. 6 Capitol attack are expected to gather.