5. Cumulus Clouds
Very common in the summer, if you are a hiker or a climber, you should be extremely cautious of these marshmallow-like clouds that look swished together in the sky. These formations clearly indicate that severe thunderstorms and lightning are on their way.
During the day, these formations build up into black, anvil-shaped clouds, usually growing faster vertically than horizontally into huge cumulonimbus cloud formations. Thankfully because these clouds build up over time, you have plenty of time to get the hell out of Dodge!