To begin, there’s no such thing as “heat lightning.” What people call heat lightning is actually legitimate lightning from a distant thunderstorm.
Brad Panovich, the chief meteorologist from the NBC affiliate in Charlotte, N.C., posted a good overview on the subject and explained its origins:
The term originated in the days when people used to sit on their front porch on warm summer evenings to escape the hotter house prior to air conditioning. It was also in an era before Doppler Radar was easily available to the public on TV, online and via mobile devices.
People would notice lightning in the sky, but they never heard thunder or saw a drop of rain and there was even clear skies over their heads. So they just called it heat lightning because it happens on warm summer nights.
Tuesday evening, I heard reports of “heat lightning” but the observers were actually viewing real thunderstorms to D.C.’s west (along the I-81 corridor) and south (near Richmond), some 60-100 miles away.
Yes, you can see thunderstorms at night from great distances because they often extend very high in the sky (up to 9-10 miles up) and lightning is, well, vivid. You will not hear such storms, though.
The National Weather Service (NWS) office in Sterling created the image below which shows the radar view of the thunderstorms to the west Tuesday evening, with an inset view of what the storm looked like in the sky some 70 miles to the east.
Steve Zubrick, the science operations officer at the NWS office in Sterling, took this video of the same storm:
Zubrick’s description: “30 sec video taken at 908 pm EDT 16 July 2013 looking west showing lightning illuminating storms over 75 miles away in the eastern West Virginia counties of Hardy and Hampshire.”
And here’s a video posted to Twitter by @RyanJKelly viewing a distant storm from Crystal City:
Finally, here’s a tremendous close-up view of one of the storms Washingtonians saw from a distance, taken from the Shenandoah Valley by photographer Edward Payne…