What Is Dew?

What You'll Learn

• Dew is tiny water drops that form on cool surfaces overnight
• During the day, water evaporates into the air as invisible vapor
• At night, the air gets colder and can't hold as much water vapor
• The extra water vapor condenses into liquid drops on cool surfaces
• Dew is most common on clear, calm nights

Words to Know

Dew

Tiny water drops on cool surfaces overnight

"The morning dew made the grass wet."

Water vapor

Invisible water in the air

"Water vapor condenses into dew at night."

Condense

When vapor cools into liquid drops

"The vapor condensed on the cold grass."

Surface

The outside of something

"Dew formed on the car's surface."

Check What You Learned

Fun Facts

• Dew is water that condenses from water vapor onto cool surfaces overnight

  Source: National Weather Service / NOAA

• During the day, water evaporates into the air as water vapor

  Source: USGS Water Science School

• Warm air can hold more water vapor than cold air

  Source: NOAA

• At night, as air cools, it can no longer hold all its water vapor, and the excess condenses into liquid droplets

  Source: NWS

• Dew forms on surfaces that cool below the dew point temperature

  Source: NOAA

• Clear, calm nights promote dew because the ground cools rapidly without cloud insulation

  Source: NWS