High-level clouds are found at altitudes above 20,000 feet (6,000 meters) and are typically composed of ice crystals due to the cold temperatures at these heights. The main types of high-level clouds include cirrus, cirrostratus, and cirrocumulus. These clouds are usually thin and wispy, often indicating fair weather, but they can also signal an approaching storm. These clouds play a role in the Earth's climate by reflecting sunlight and trapping heat. High-level clouds can create beautiful optical phenomena, such as sun dogs and halos, which occur when sunlight interacts with the ice crystals in the clouds.