A significant heatwave, driven by a powerful heat dome, is currently affecting much of the United States, with more than 100 million people under heat alerts. Conditions have escalated to dangerously high temperatures, with heat indices reaching as high as 115 degrees in some areas, particularly in the Midwest and South. Cities like St. Louis are facing record temperatures while severe storms threaten to disrupt travel. Despite the oppressive heat, a cooldown is anticipated later in the week. Authorities are urging residents to take precautions against heat-related illnesses, for both people and pets, amid rising humidity and increased power demand.