What kind of clouds are typically formed at high altitudes and indicate fair weather?

Cirrus clouds are typically formed at high altitudes, usually above 20,000 feet. These clouds are characterized by their wispy, feather-like appearance and are composed of ice crystals. Their presence often indicates fair weather, especially when they appear isolated. As they are formed in the upper troposphere, they can signify that the air is stable and dry in that part of the atmosphere. Sometimes, cirrus clouds can also be a sign that a change in weather may be approaching, but they primarily indicate good weather conditions during their formation.

Cumulus clouds, on the other hand, are more associated with fair weather but typically form at lower altitudes and can develop into larger cumulonimbus clouds, which indicate thunderstorms. Nimbus clouds, notably nimbostratus, are associated with precipitation and therefore do not indicate fair weather. Stratus clouds, while they can be widespread and cover a large area, are often linked to overcast conditions and light rain or drizzle rather than clear weather.