just high altitudes
cirrus
Cirrus clouds.
Cirrus clouds are comprised of ice crystals so they are found at high altitudes.
Cirrus clouds are thin, wispy clouds usually formed at high altitudes.
cirrus
Cirrus cloud
cirrus
Cirrus clouds are high altitude clouds occurring between 17,000 and 40,000 feet
Cirrus clouds are high-level clouds. They form at altitudes above 20,000 feet (6,000 meters) in the Earth's atmosphere and are typically composed of ice crystals. These clouds appear thin, wispy, and high in the sky and are often associated with fair weather or the approach of a warm front.
cirrus clouds
Cirrus Clouds
Lacy clouds that form at high altitudes are cirrus clouds. These types of clouds usually form before there is a change in weather. These clouds form above 20,000 feet, and they indicate fair weather.