One of the memorable experiences I’ve had in my life was during a road trip that my husband and I and another couple took through the Southwest. We were driving along a highway in Arizona, with flat land all around us. In the distance we could see black clouds and streaks of rain falling, although there was no rain falling where we were. Just about the time the lightning began in that distant storm, we came upon a herd of wild horses running parallel to the road we were on. The wild horses running, with the lightning and storm in the distance, took my breath away. Some moments are like that.
I like lightning and get to see plenty of it here in the North Country. The past couple of days I have stayed up late watching heat lightning. I always thought that heat lightning was a phenomenon that somehow resulted from static electricity building up in hot, humid air. Now I find out that’s an old wife’s tale. Although I am an old wife, I was surprised to learn that what we think of as heat lightning is actually lightning from a storm far away from us. It’s common during the summer when the weather is sultry because the sky is frequently hazy. Light from thunderstorms as far away as 100 miles can be reflected off layers of haze and reflected into the sky. We don’t hear the thunder because the sound only travels about 10 miles, or may be blocked by nearby terrain. Sound waves can also be refracted upward by the hot and cold temperatures around a thunderstorm.
Lightning is caused by the buildup of static charges in clouds. During a storm, particles of rain, ice, or snow collide, producing negative charges in the lower levels of storm clouds. Objects on the ground become positively charged and the imbalance results in current passing between the two charges. Lightning is extremely hot. A flash of lightning can heat the air around it to temperatures several times hotter than the sun. This heat and the subsequent cooling causes the surrounding air to expand rapidly and vibrate, which results in the cracking and rumbling of thunder.