Early estimates indicate that most of the contiguous United States will see highs running 10 to 15 degrees above average. When combined with climbing humidity, it’ll feel like it’s well into the triple digits for millions. The pattern could also spark severe thunderstorms, perhaps packing strong winds, that could roll through the northern Great Lakes and New England during late July and August.
On Friday, most of the heat was relegated to the north central United States, where temperatures in the Dakotas were forecast to near 100.
Billings, Mont., has already measured 13 days topping 95 degrees this month. Monday spiked to 107 degrees, a degree shy of an all-time record. With highs in the upper 90s to lower 100s projected every day over the coming week, it is possible that tally may climb to near 20 by the end of July. That would mark the most 95-plus degree days in Billings in July since 1936.
Next week’s heat wave looks to be more impressive in duration than in magnitude. Heat advisories are in effect for parts of Minnesota and the Upper Midwest, the Plains and Corn Belt and along the Gulf Coast.
In addition to daytime highs in the upper 90s with heat indices reaching 105 degrees, nighttime lows will struggle to drop.
“Overnight lows will not cool to less than 70 to 75 degrees,” warned the Weather Service in Kansas City, where an excessive heat warning is in effect. “This will make the recovery from daytime heat tougher to overcome.”
The temperatures could favor an increased risk of heat-related illnesses, such as heat exhaustion and heat stroke.
Heat will intensify this weekend, bringing highs in the upper 90s to near 100 to the Dakotas. That’s just an appetizer, however. The main heat event, which will occupy a much larger swath of the western and central United States, will just be getting started by then.
On Monday and Tuesday, a renewed pulse of heat will began to gather in the Pacific Northwest and north Intermountain West. This represents the first signs of a building heat dome that will drape itself across most of the Lower 48 by midweek.
By Wednesday, the heat dome should stretch from the Pacific Coast to the Appalachians, with hazy and hot temperatures just about everywhere in between. The National Oceanic and Atmospheric Administration’s Climate Prediction Center indicates odds of near-average to above-average temperatures for the entire contiguous United States.
It’s too early to give specific numbers, but the Plains could see temperatures in the mid- to upper 90s or lower 100s as the heat wave builds. Temperatures could reach into the mid- to upper 90s in the Southeast and top 100 for many regions in the West.
On Tuesday, Oklahoma City and Omaha will both hover near 100. Billings could hit 106 degrees and Bismarck may see 102. That’s as hot or hotter than Phoenix will be.
On Thursday, Kansas City is forecast to hit 100 degrees, while St. Louis could spike to 97. Neither represent an outlandish or record temperature, but highs could run well above average into August.
Heat domes are zones of high pressure that deliver sinking air, which warms and dries as it subsides. A heat dome can also help bring clear skies, while deflecting clouds and storm systems around it. That allows for additional sunshine, reinforcing heating.
Since heated gases expand, in this case vertically, the “halfway point” of the atmosphere’s mass may wind up nearly a football field higher than average next week.
While nearly everyone will be basking in summertime toastiness, a few areas will trend closer to average. Early week monsoonal moisture may linger over the Desert Southwest and Four Corners region, keeping temperatures a bit more modest as afternoon showers and thunderstorms brew.
Another area to watch that may not fully tap into the heat will be parts of New England. Computer weather models hint that a lobe of cool air may hang around at high altitudes, keeping surface temperatures closer to average. In between there and the heat dome, a corridor of thunderstorm activity may crop up; the jet stream pattern would favor strong winds.
The greatest risk for strong to severe storms during this period would be from the northern tier and Upper Midwest through the Great Lakes region and into the Northeast. Multiple waves of strong to severe thunderstorms are possible, bringing pockets of heavy rain to an already-waterlogged area.
While heat domes are normal staples of the summer, the duration and intensity of said heat events is on the rise in tandem with warming global temperatures thanks to human-induced climate change.
Just last month, a thousand-year heat event that would have been “virtually impossible” without climate change brought temperatures of 108 degrees to Seattle and 116 degrees to Portland, Ore. Lytton, B.C., broke the Canadian national temperature record three days in a row, hitting 121 degrees before the town burned down in a cataclysmic wildfire.
Meanwhile, much of the United States has spent days veiled by a layer of wildfire smoke poured into the skies by hundreds of blazes in western North America, including the 400,000-acre Bootleg Fire in southeastern Oregon. Climate change continues to accelerate drought conditions taking hold of the West, fostering more favorable fire conditions and more extreme wildfire behavior.
This story was posted July 22 and updated July 23.