After breaking countless July heat records across the Plains and Mississippi Valley, more of the same can be expected today. While it will be the extreme heat`s last gasp for the Missouri and Ohio valleys, nearly the entire length of the rolling Plains will bake in a triple-digit heat wave into this upcoming weekend. While the heat has graciously come to an end for those across the record-shattering Mid-Atlantic and Northeast Wednesday, the dangerous heat will move forward like a high octane gas running a car for Plains residents through the upcoming weekend. Widespread 90s will cover more than 1,500 miles from South Texas to the Canada and U.S. border, with triple-digits a staple from north Texas to southwestern South Dakota. Fortunately, this will be the final punch of excruciating heat for the Missouri and Ohio valleys today. A storm system sliding from the Ohio Valley into the Mid-Atlantic will drag cooler, Canadian air southward in the wake of a cold front. Instead of blistering 90s and lower 100s for highs, the mercury will slide back into the more tolerable 70s and 80s for Friday. At the core roots of this extended heat spell is a stubborn upper-level high pressure. Although it`s being buckled across the Missouri and Ohio valleys, it will just relocate further west across the Plains. In turn, it will transport very hot and humid air northbound on southwesterly breezes and provide no relief for the widest covering U.S. drought since 1956. Unfortunately, this will mean an unfavorable hot outcome for Plains residents for the foreseeable future. Heat Advisories and Excessive Heat Warnings remain in place from the U.S. and Canada border to southern Arkansas and western Ohio. Kansas City, Mo., St. Louis, Cincinnati, Louisville, Ky., Memphis, Tenn., Little Rock, Ark., Topeka, Kan., Valentine, Neb., Rapid City, S.D., and Bismarck, N.D., are all included in these heat-related advisories. Add in the oppressive humidity and the heat index, or a measurement of what it feels like to the body, will easily exceed 105 degrees from the Plains to Ohio Valley today. Stay hydrated by drinking plenty of water. Make sure to frequently check on at-risk groups, including pets, the homeless, young children and the elderly. If you must be outdoor for any length of time, take these preventative maintenance tips when dealing with the extreme heat. Before the weather turns 180 degrees for just a short-lived time late this week in the Missouri Valley, St. Louis could tie or break its record high of 106 degrees set back in 1934. Paducah, Ky., will also make one final run at record territory, challenging its 102-degree record. Even as far north as Bismarck, N.D., could break its record of 100 degrees set last in 2005. Be sure to keep WeatherBug active to receive the latest weather in your neighborhood and get the latest updates anywhere on Twitter. What do you think of this story? Click here for comments or suggestions.