 Good morning, I'm Michelle Bash. And I'm John Aaron. Teddy Gellman is our producer. The top story we're following is the extreme heat continuing again today. An excessive heat warning is in effect for the immediate D.C. area starting at noon. Also starting at noon, a heat advisory in effect for the rest of the region. Now, we asked National Weather Service meteorologist Eric Taylor how the agency makes the determination, the determination that is, to issue an excessive heat advisory.