A sprawling heat dome is expected to bring dangerous temperatures to much of the Lower 48 beginning this weekend, with forecasters warning the prolonged event could last at least a week and linger even longer in some areas.
Why it matters:
Millions of Americans could face temperatures 15 to 25 degrees above average. Elevated overnight temperatures will limit relief, increase health risks and worsen wildfire conditions.
By the numbers:
More than 90 daily temperature records could be tied or broken through Wednesday, according to the National Weather Service. Roughly two-thirds of those records involve unusually warm nighttime lows.
Driving the forecast:
A strong dome of high pressure centered over the Northern Plains will trap heat across as much as two-thirds of the continental United States before expanding eastward over the next 10 days.
Climate scientists say human-caused climate change is increasing the intensity, duration and geographic reach of extreme heat events. Recent El Niño conditions are not expected to play a major role in the current outbreak.
What to watch:
Record-breaking nighttime warmth is forecast from Texas to Florida and into the Carolinas, where temperatures may remain above 80 degrees overnight. Dangerous heat could persist into late July across parts of the country.
