Another heat dome of high pressure will spread dangerous heat and humidity from the South into parts of the Midwest this week. While the upper Midwest and Northeast will see a reprieve from summer's searing temperatures over the next few days, July's reputation for oppressive heat and muggy air will be on display as the week wears on. And that could have real staying power for some. Here are the main takeaways from the forecast: (TRACK THE HEAT:Temperatures|Heat Index) - Heat and oppressive humidity will gradually build in the parts of the South, the lower and mid-Mississippi Valleys through the early part of the week. - Beginning Tuesday, hotter, more humid air will spread into parts of the Midwest, especially the Ohio Valley, but also parts of the Great Lakes. - At least somewhat hot and humid air may also stretch into parts of the Northeast as soon as Wednesday. - We're not expecting nearly as many daily record highs as we saw in thelate June heat wave. But that's because we're around thehottest time of yearin parts of the South, Midwest and East, so setting new daily record highs this time of year is more difficult. - But that doesn't mean it won't be dangerously hot. By mid-week, 90s will have spread from the South into the lower Midwest. By late in the week, at least some 90s are possible in the Northeast. - Parts of the South could see triple-digit highs for several days in a row, including Texas, Oklahoma, northern Louisiana, Arkansas and Missouri. - And overnight lows in the middle to upper 70s will become increasingly common as the heat wave builds. That won't allow much heat relief at night for those without access to air conditioning. There will be numerous record overnight warm temperatures in the Southeast. (MAPS:10-Day US Forecast Highs and Lows) - This heat will be accompanied by oppressively muggy air particularly in the Mississippi and Ohio Valleys. - Some dew points in these areas could rise into the upper 70s or even low 80s, about the muggiest air can get in these areas in summer. - Some muggy air (70s dew points) may also be pulled north into the upper Midwest and Northeast, at times. (MORE:What The Dew Point Means) - Unfortunately, this heat wave may have staying power into at least the last weekend of July in the Plains and South, while slowly expanding west toward the Rockies. - Our longer range outlooks suggest the Northeast has the best chance of eventually seeing some heat relief around that last weekend of July. (MORE:Should You Turn Off Your A/C Or Leave It On When You Leave Home?) -Heat is the No. 1 weather killer in the U.S., with hundreds of fatalities each year. - The combination of heat and humidity lingering into the night for several days in a row is dangerous for those without access to air conditioning, especially in the cores of larger cities. - Check on family, friends, the elderly and those with chronic illness who live without access to air conditioning. - If possible, avoid being outdoors for long in the peak heat of the afternoon. - If not, take frequent breaks, avoid strenuous activity, drink more water than usual and wear loose, lightweight clothing. (MORE:Heat Advice From An ER Doctor) - A strong bubble of high pressure aloft known as aheat domeis forecast to develop. - Sinking air near the center of this heat dome suppresses clouds, allowing the intense sunshine this time of year to heat the ground and air above it most efficiently. - Southerly winds on the western periphery of the heat dome pull increasingly hot and humid air north, then may circulate that oppressive air eastward on its northern rim, sometimes fuelingclusters of thunderstorms with flooding rain and/or high winds. Jonathan Erdman is a senior meteorologist at weather.com and has been covering national and international weather since 1996. Extreme and bizarre weather are his favorite topics. Reach out to him onBluesky,X (formerly Twitter)andFacebook.
