Can evaporation occur at 100% humidity?

Can Evaporation Happen at 100% Humidity?

When you look outside on a thick, foggy morning, you might wonder if water is still drying up into the atmosphere. The short answer is no, net evaporation cannot occur when the relative humidity reaches 100 percent.

Humidity measures how much water vapor is currently suspended in the air. When that air is completely saturated—meaning it has hit 100 percent capacity—it simply cannot hold any more moisture. Think of it like a sponge that is already soaking wet; try to pour more water on it, and it just pools on the surface instead of being absorbed.

In this saturated state, water molecules are constantly moving back and forth between the liquid and gas phases. However, the rate of condensation (water vapor turning back into liquid) completely matches or exceeds the rate of evaporation. This delicate balance is why your clothes refuse to dry on a damp, muggy day, and why sweat just sits on your skin instead of evaporating to cool you down.