National Weather Service forecast for the maximum heat index on Saturday. (weatherbell.com) A heat wave featuring a life-threatening combination of heat and oppressive humidity has begun to spread across the United States, with excessive heat warnings and heat advisories in effect for at least 22 states and the District of Columbia. According to the National Weather Service, 51 percent of the Lower 48 states are likely to see air temperatures reach or exceed 95 degrees during the next seven days, with 85 percent experiencing temperatures above 90 degrees during the same period. Washington could see its first high temperature at or above 100 degrees since 2016. In Chicago, the air temperature is also forecast to approach the century mark. The heat index, which is a measure of how hot it feels to the human body when air temperatures are combined with the amount of moisture in the air, are […]