BY HANNES THUM
Since I was a kid, I have always loved late-summer thunderstorms. Sure, it doesn’t feel good to get caught in one above treeline. And, sure, they can cause all sorts of destruction and chaos when they are at their worst. But, when the afternoon thunderstorms begin to build in this Valley in August, when the clouds grow and grow on the horizon until they suddenly darken the whole town as the wind whips up, and when you first see a bolt of lightning rip across the sky (the same sky that was clear and blue just a half hour earlier!) and you hear that first rumble of thunder… well, I find it pretty exciting. If nothing else, the storms give us a break from the heat of the summer sun.
Importantly, it is the summer sun itself that spawns these storms. At its most basic level, a thunderstorm is caused by some air going up and some air going down—the electrical charge built up by the vertical cross-movement of air is what causes lightning and thunder to occur.
And, one of the best ways to create vertical movement of air in our atmosphere is to heat the heck out of the air down near the ground—which the intense August sun is pretty good at doing. The air heated near the ground goes up into the sky, a cloud forms because of the moisture it is carrying, the rain comes down, molecules going up rub against molecules going down… and there you have it. The energy releases as lightning. Thunderstorm!
Lightning, of course, often means fire. That’s particularly true in August when the sun has drawn a lot of the moisture out of the land, and the wind blows hot and dry.
On July 22, a powerful thunderstorm came through our area before moving on into the Snake River Plain, where it ignited a lot of separate brush fires that evening. We heard the thunder in Hailey but wouldn’t hear about the resulting ignitions until the next morning.
Most of these almost-simultaneous lightning starts were contained quickly by BLM and local fire crews in the areas, but one of these fires, which came to be named the Sheep Fire, would burn more than 100,000 acres in the first two days.
A week later, a simmering storm that had spent much of the day quietly darkening the skies of the north Valley finally let loose with a long series of lightning bolts and thunder claps as evening approached. At least two new fire starts would be reported in our northern county from that storm.
So, it is worth being wary of the ominous storms—any one of those bolts of lightning can create a new fire. But, I still look forward to seeing them build on the horizon on these hot days when the energy in the atmosphere reaches a tipping point. And I enjoy hearing the thunder roll on down the Valley.
Hannes Thum is a Wood River Valley native and has spent most of his life exploring what our local ecosystems have to offer. He currently teaches science at Sun Valley Community School.