AccuWeather.com reports triple-digit heat that has been reserved for the Plains so far this summer is spilling east and will even make an appearance along parts of the I-95 corridor today.

Along with the searing heat, an uptick in humidity will make outdoor conditions downright dangerous, especially for those with health issues.

AccuWeather.com RealFeel® temperatures, which measure how "hot it feels" based on air temperature, humidity and the strength of sun’s rays, will easily exceed 100° in a large part of the Mississippi Valley and East again today.

In fact, RealFeel® temperatures in Louisville, Ky., were already in the 100s early this morning and hit 111° around 8 a.m. EDT!

Other select areas will have to suffer through RealFeel® temperatures of 110° or higher today as well.

The oppressive heat and humidity is thanks in part to a large area of high pressure sitting over the middle part of the Mississippi Valley. Expert Senior Meteorologist Alex Sosnowski warned us a few days ago that this feature would crank up the heat for the beginning of this week.

High temperatures well into the 90s will encompass areas from the central Plains to the mid-Atlantic today. Many cities from Wichita, Kan., to Oklahoma City, Okla., Dallas, Texas, Little Rock, Ark., Memphis and Nashville, Tenn., and Charlotte and Raleigh, N.C., will have their thermometers approach or exceed 100° by late this afternoon.

This map shows just how large the area of the country is that will be experiencing AccuWeather.com RealFeel® temperatures in the 100s (dark red) today.

Even areas farther north along the Interstate 95 corridor, including Richmond, Va., and Washington, D.C., could approach 100°, though RealFeel® temperatures will easily exceed that number across a wider area.

Many of these areas have been sizzling since the weekend. Wichita broke a record high by reaching 111° on Sunday, with several other communities throughout the Plains topping out between 105° and 110°.

One thing consistently observed with this heat wave thus far is that temperatures can go unpredictably higher and exceed forecasters’ expectations. Because of this, it’s not out of the question that the 100-degree area forecast today could be larger in actuality.

While only shade, water and air conditioning will offer relief from sizzling days, don’t expect much relief at night. Low temperatures in the 70s, and even near 80 in blacktop havens (cities), will make sleeping uncomfortable for those without air conditioners.

During the day, please be sure to take frequent breaks and drink plenty of non-alcoholic fluids if you must work outdoors. Because of the bright sunshine, be sure to frequently reapply suntan lotion.

The elderly, infirm and those with health issues are more susceptible to succumb to heat-related illness, such as heat stroke. These individuals should be checked on frequently.

Fortunately, relief is on the way by midweek for some, as pointed out by Meteorologist Brian Edwards. A cold front crashing south across the Midwest and Northeast will provide some cooling, but also spark locally strong thunderstorms again.

Behind the front, temperatures will drop at least 10 degrees across the Ohio Valley and mid-Atlantic, while humidity plunges as well. However, areas farther south will remain hot, albeit in the 90s rather than the low 100s.