Between what altitudes in kilometers do Venus's main cloud deck lie?

Venus’s main cloud deck lies approximately 50 to 70 kilometers above the planet’s surface. This enormous, planet-wide layer is made primarily of sulfuric-acid droplets and is responsible for Venus’s permanently cloudy appearance.

The cloud system is not a single flat sheet. It contains several layers, with the densest region near about 48.5 kilometers and higher cloud layers extending toward 70 kilometers. On the dayside, the principal cloud deck is roughly 20 kilometers thick; on the nightside, high-altitude haze can reach substantially farther upward.

Conditions near the lower and middle cloud levels are far less extreme than at the surface. Around 50 to 65 kilometers altitude, temperature and pressure can resemble conditions near Earth’s surface, although the air is mostly carbon dioxide and the clouds are strongly acidic. This has made the region a subject of interest for atmospheric research and speculative future exploration.

The upper cloud deck also drives Venus’s famous super-rotation. Winds near 60 to 70 kilometers altitude can reach about 100 meters per second, circling the planet far faster than the solid surface rotates. The clouds therefore provide a visible tracer of Venus’s extraordinary atmospheric circulation.