Yet another brutal heat dome is set to scorch parts of the United States starting this weekend as part of a major weather pattern shift.
Last week, the East Coast was hit by a heat wave, followed by the West Coast, which is facing a heat dome, a vast area of high pressure that lodges over the region, trapping heat and raising temperatures.
During the hottest month of the year, maximum temperatures are expected to rise 10 to 15 degrees above normal, reaching triple digits in some places. If the heat wave continues again, concerns about wildfires may also increase.
Some of the most severe heat will be concentrated in the Rocky Mountains, where daily records could be tied or broken, and some locations could come within a few degrees of record highs.
Dangerous heat waves could move into the central United States early next week as the heat dome expands, but it will be several days before the forecast becomes reliable.
Heat has long been the deadliest weather condition in the United States, but the threat is increasing. Heat waves now last longer, are more intense, and are more likely to occur due to emissions from fossil fuel combustion.
A rapid investigation into the cause found that the combination of extreme heat and high humidity seen in East Coast heat domes last week would not have been possible without greenhouse gas emissions.
Here’s what we know:
Ahead of the pattern change, the remainder of this week will be seasonably warm across much of the West. Temperatures will begin to rise to even more uncomfortable levels on Friday as a widespread area of high pressure develops. As the heat dome strengthens, it will shift the jet stream (the river of air that determines where severe weather occurs) from the United States to southern Canada.
Widespread high temperatures in the upper 90s to low 100s Fahrenheit are expected Saturday from the Rocky Mountains to eastern Oregon and parts of California. Areas along the west coast will avoid the worst of the heat.
The heat is expected to get even stronger on Sunday, with highs near 105 degrees in parts of Montana, Wyoming and the Dakotas.
Temperatures are expected to reach around 103 degrees in Billings, Montana, on Saturday. That could threaten the city’s all-time high of 108 degrees on Sunday.
Salt Lake City and Grand Junction, Colorado are in a similar situation. Salt Lake City’s high temperature was 107 degrees, with highs expected to reach 103 degrees on Saturday and 105 degrees on Sunday. Grand Junction’s high temperature was about 104 degrees on Saturday and 106 degrees on Sunday, close to the city’s all-time high of 107 degrees.
The heat will increase next week
The scorching weather will move farther east by Monday, reaching more areas of the Rocky Mountain foothills and plains.
Monday and Tuesday could be the hottest days ahead for the Denver area, with highs potentially reaching triple digits. The city’s all-time high temperature record was 105 degrees.
Heat will spread into parts of the Midwest on Tuesday and Wednesday, and the northern Plains and Rocky Mountains will continue to be hot.
Temperatures in Minneapolis are expected to reach 90 degrees next week, about 10 degrees warmer than normal.
The heat in the western and central United States is likely to continue into next week, with heat domes breaking down more slowly over time.
What the heat dome means for wildfire activity in the West is less clear.
Wildfires have burned more than 3.3 million acres in the United States so far this year, which is well above average. Most of this fire activity is occurring in the West, with destructive fires breaking out in parts of Colorado and Utah in recent weeks.
Normally, such heatwaves dry out plants and make them more prone to fire, but drought-stricken areas are already very dry.
Hot, dry conditions are a concern for fires, but heat domes are large areas of high pressure, so gusts of wind that could fan flames are unlikely for the foreseeable future.
An expanding heat dome could also bring moisture to parts of the Rocky Mountains next week as winds shift from the south. This surge in moisture could keep temperatures from rising, but it could also encourage thunderstorm development and lightning strikes.
We will continue to monitor how this pattern change impacts wildfire activity.
CNN’s Andrew Friedman contributed to this article.
