At least 40 million people were under extreme heat warnings across central and southern parts of the United States on Sunday as high temperatures and severe humidity gripped large swaths of the country for a second straight day.Heat indexes exceeding 105 degrees Fahrenheit (40.5 Celsius) stretched from Minnesota down to Mississippi, extending west into southern California and Nevada. Parts of the southwest could see highs of 120 degrees Fahrenheit (49 C) on Sunday, according to the National Weather Service.Meteorologists said the sweltering weather was the result of another heat dome — a phenomenon in which atmospheric conditions trap heat, accentuating and prolonging already high temperaturesOn Saturday, Rapid City, South Dakota, reported an all-time high of 112 degrees Fahrenheit (44 C). A horse race planned in Canterbury Park, in Shakopee, Minnesota, was canceled Sunday because of the heat.“Right now, it’s affecting a lot of people right in the middle of the country,” said Bob Oravec, an NWS meteorologist.
“The core of the heat sinks southward by early next week.”The moist air was also producing other volatility around the top of the heat dome, including the risk of severe thunderstorms, flash flooding and hail around the Great Lakes on Sunday. The potential for heavy storms was expected to move east in the coming days.“If you have a heat dome in one part of the country, you’ll have a different corresponding weather in another part,” Oravec said. “It’s all related.”Temporary relief will come to the central U.S.
toward the middle of the week, but high temperatures could return by the weekend, he noted.Authorities warned that children and older adults, along with people with certain medical conditions, are especially at risk of serious reactions including heat stroke. Experts recommend seeking out air conditioning or a cooling center, make sure to drink enough water and limit time under the direct sun.The continental U.S. endured the second-hottest first half of the year on record in 2026, according tracking of average temperatures by the National Centers for Environmental Information.
Another hot day is in store for San Diego County, with temperatures running well above average before a slight cooldown arrives early next week. While conditions ease for a few days, forecasters say the hottest weather of the summer could arrive by the end of the week.A few light showers are possible early Sunday morning, mainly across the South Bay and southeastern San Diego County, as a pocket of tropical moisture moves through the region. Most neighborhoods will remain dry, and any clouds will clear by late morning, allowing temperatures to climb quickly through the afternoon.Highs today will reach the upper 70s to low 80s along the coast, the mid-80s to mid-90s inland, the upper 80s to mid-90s in the mountains, and 108 to 115 degrees in the deserts.
That's about 8 to 12 degrees above average for late July.A Heat Advisory remains in effect through Monday evening for the coast, inland valleys, and mountains, while an Extreme Heat Warning continues for the deserts.There is some relief on the way. Temperatures will gradually cool Sunday through Wednesday, dropping to around 5 degrees above normal by the middle of the week. Even with the cooldown, afternoons will still feel warmer than what is typical for this time of year.The break won't last long.High pressure is expected to strengthen again beginning Thursday, sending temperatures back upward.
Forecast confidence is increasing that Friday and next weekend could bring the hottest weather San Diego has experienced so far this summer, with many inland communities reaching 10 to 15 degrees above average.Beachgoers should also be prepared for rougher ocean conditions.A long-period south swell will build through the first half of the week, bringing 3 to 5-foot surf Sunday, increasing to 4 to 6 feet with occasional sets up to 7 or 8 feet Monday and Tuesday, especially at south-facing beaches. A high risk of rip currents will continue through much of the week, and elevated high tides could lead to minor coastal flooding during the evening high tide cycle.Sunday's Forecast Highs Coast: Upper 70s to low 80s Inland Valleys: Mid-80s to mid-90s Mountains: Upper 80s to mid-90s Deserts: 108 to 115
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