In Silver Spring, Md., on Monday, Matt MacCartney was one of many workers dismantling fallen trees that took down power lines. Chip Somodevilla/Getty Images hide caption

itoggle caption Chip Somodevilla/Getty Images

Where you're most likely to be in the path of a derecho, and how often. National Oceanic and Atmospheric Administration hide caption

itoggle caption National Oceanic and Atmospheric Administration

Doug Jones, owner of Piedmont Biofarm in Pittsboro, N.C., waters vegetables as temperatures in the South soar, Friday, June 29. Triple-digit temperatures are expected for several days in North Carolina. Gerry Broome/AP hide caption

itoggle caption Gerry Broome/AP

Branches and power lines littered the nation's capital after bruising storms swept through the Mid-Atlantic region on Friday night. Win McNamee/Getty Images hide caption

itoggle caption Win McNamee/Getty Images

Before the start of the Boston Marathon this morning, a runner grabbed a bottle of water from among the hundreds lined up on a table in Hopkinton, Mass. Stew Milne/AP hide caption

itoggle caption Stew Milne/AP

This photo provided by the Amarillo/Potter/Randall Office of Emergency Management shows Potter County firefighter Matt Dryden standing next to a wall of hail on Wednesday near Amarillo, Texas. The hail was pushed into drifts of up to 4-feet. AP hide caption

itoggle caption AP