Lightning!
We had some thunderstorms move through the St. Louis area last night just as it was getting dark. At first the storm clouds were reflecting the rays of the setting sun, causing them to be a strange yellowish-orange color overhead as the rain poured down (sorry, no photos). Several minutes later when it was darker the lightning started.
We get thunderstorms quite regularly here, and although this wasn't a system that was strong enough to spawn tornadoes, dump loads of hail, or have frightening winds (at least around us -- perhaps it was worse in other parts of the city?) one thing it did have was lightning. An amazing amount of lightning.