Nearly half of continental US in throes of brutal heat wave

Residents from the California valleys to the Mississippi River are bracing for temperatures near- to well-above 100 degrees Fahrenheit expected to last into mid-July.

Brutal heat has been baking the southwestern U.S. since early last week. Phoenix, Arizona, has experienced high temperatures of 110 degrees or more since July 4, and cities like Las Vegas and Bakersfield, California, soared above 100 degrees for several days.

Excessive heat warnings were put into place until Monday evening, from Southern California to southeast Arizona. Heat advisories on Saturday extended even farther east, from southern New Mexico to the Florida Gulf Coast.

A northward bend in the jet stream will continue to help keep the heat locked over the Southwest and also allow it to nudge eastward into the south-central U.S. through the middle of the week.

High pressure settling under this jet stream will limit showers and thunderstorms, leaving communities to bake in the unobstructed sunshine.

"Ongoing and worsening drought over the southwestern United States will also continue to contribute to well-above-average heat into early week," said AccuWeather Senior Meteorologist Alex Sosnowski.

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On Sunday, Las Vegas recorded its highest temperature of the year thus far when the city soared to 113 degrees. However, Las Vegas fell just 1 degree short of tying the record high for the day, last set in 2003.

The mercury in Phoenix, Arizona, climbed to 116 degrees on Sunday and broke the record of 115 last set in 2009. As if record-breaking daytime high temperatures weren't enough, abnormally warm low temperatures are not offering any relief. The mercury has not fallen below 90 degrees since July 7 in Phoenix.

With a low temperature above 90 degrees in the city on Monday morning, Phoenix has tied the second longest streak for low temperatures above 90 degrees of all time for the city with 6 days. The all-time longest streak is 7 days, set from August 7-13 in 2012.

Even Palm Springs, California, got in on the record-breaking action on Sunday. Palm Springs soared to a sweltering 121 degrees on Sunday and broke the previous record of 120, last set 35 years ago.

None of those locations came close to Death Valley National Park in California, however. The mercury topped out at 128 F on Sunday shortly after 5 p.m. local time, and in fact, it never dropped below 100 as the low for the day was 100 F.

Temperatures will continue to soar as much as 10 to 15 degrees above normal across parts of Nevada, Utah, Arizona, Colorado and New Mexico into Tuesday.

Daily record highs will continue to be challenged, but temperatures could even come to within a few degrees of all-time record highs set as far back as the Dust Bowl era of the 1930s.

AccuWeather RealFeel® Temperatures will be several degrees higher in the sun, and could be as much as 20 degrees higher or more above the actual air temperature.

While a few locations could see some thunderstorms firing courtesy of an uptick in monsoon moisture, most locations will stay dry until a more robust push of moisture comes in around midweek. The persistent heat, and lack of rainfall in many of these areas will continue to worsen any drought conditions, and keep brush dry. Both could make it easier for any spark to quickly become a wildfire.

As the week progresses, the heat will continue to spill eastward into the southern Plains. On Monday, Amarillo and Lubbock in northwestern Texas both set all-time record high temperatures for the month of July at 110 degrees. For Lubbock, Monday became one of the top seven hottest days of all time.

Amarillo and Lubbock will continue to top out above 105 degrees through Tuesday, more than 10 degrees above the norm in mid-July. Even as far north as Dodge City and Wichita, Kansas, will reach over 5 degrees above normal into the upper 90s into Wednesday.

Higher humidity levels, soil moisture and scattered thunderstorm activity will prevent 110- to 120-degree heat in the southern Plains, but it is possible that some locations approach the century mark. Widespread highs in the middle 90s are likely.

Still, even this lesser heat will be sweltering, and can be dangerous for strenuous outdoor activities. Without remaining constantly hydrated and avoiding being outside in the afternoon, heatstroke can easily sneak up on some people.

"When combined with higher humidity levels, it could feel worse to some people when compared to that of the Southwest, especially in heavily urbanized areas where there is little breeze during the afternoon and early evening hours," Sosnowski added.

Behind the extreme heat, near-normal temperatures will fill in across the West, and even parts of the northern Plains. Residents should still be vigilant with remaining hydrated and protecting their skin from the sun's strong, summer rays.

The dome of above-normal temperatures may lose some potency as it tries to charge into the East. Still, some areas across the Northeast could see a few days of higher temperatures at the end of the week.

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