Look for a sudden shift in the cloud layer’s color – a bright, almost white rim that moves faster than the rest of the sky. If the clouds start to lean in the same direction as the wind, that’s a sign the storm is moving toward you. Keep an eye on the horizon too; if you see a low, dark line that’s getting thicker and taller in a few minutes, it’s a thunderhead forming. The trick is to spot that change before the first flash, so you can move to cover or wait it out.