Last week, a “thousand-year” heat wave baked the Pacific Northwest and adjacent British Columbia with widespread highs topping 100 degrees, resulting in a death toll in the hundreds. Lytton, Canada, climbed to 121 degrees and established new national records three days in a row before the town burned in heat-intensified wildfires.

Now the West is bracing for another heat wave, albeit not quite as severe, that could challenge records and bring dangerously hot temperatures from the California and the Desert Southwest to the Great Basin and Oregon. It will mark the third punishing heat wave in the West this summer, counting the record-breaking event in mid-June.

The relentless heat is also reinforcing drought that continues to reshape landscapes and severely burden water resources, while simultaneously setting the stage for a potentially disastrous wildfire season.

The big picture

On Thursday, the heat was already beginning to gather, but the worst was expected Friday into Monday. At least 28 million people are slated to experience highs in the triple digits over the upcoming week.

The exceptional temperatures are thanks to a “heat dome,” or a ridge of high pressure, becoming established over the Four Corners region. It will meander west in the coming days, reinforced by a secondary zone of high pressure cresting to the north in southwest Canada on Friday. By Saturday, that additional high pressure will swing through Alberta and Saskatchewan; the synergy between the two will yield a multiday stretch of highs 20 degrees or more above average.

Image without a caption

Excessive heat warnings blanket most of California, Nevada, western Arizona and western Utah, while watches cover interior parts of Oregon and southern Idaho.