A heat advisory is issued when the heat index is forecast to reach 105, whereas an excessive heat warning is issued for hazardous heat indices of 110 or higher.
The advisory was not upgraded to a warning in the northern and eastern suburbs of D.C. (including Prince George’s, Montgomery, Howard, and Anne Arundel counties), nor in the suburbs of Baltimore - where heat indices may remain just under warning levels.
An excessive heat warning means a prolonged period of dangerous heat will occur. You are urged to drink plenty of fluids, stay in air-conditioning, stay out of the sun, and check on relatives and neighbors, especially older adults and the sick. Outdoor workers should take special precautions to reschedule strenuous activity to early and late in the day and hydrate liberally.
The record high today of 101 at Reagan National airport, set in 1934, is likely to be threatened. The all-time June high of 102, set in 1874 and 2011 is also in jeopardy.
These conditions have arisen from massive, record-setting heat dome sprawled across the eastern half of the U.S. Heat advisories or heat warnings are in effect in 25 states and the District.