Dew Point

The dew point is the temperature at which air becomes so full of moisture that water starts to form. When air cools to the dew point, water vapor turns into tiny droplets. This is why you see dew on grass in the morning. It is also how fog and clouds form.

How Dew Forms

At night, the ground cools down and so does the air near it. When the air temperature drops to the dew point, the water vapor in the air turns into liquid droplets. These droplets appear on grass, car windows, and spider webs. If the dew point is below freezing, you get frost instead of dew.

Dew Point and Comfort

The dew point tells you how muggy the air feels. When the dew point is below 55 degrees Fahrenheit, the air feels comfortable. Above 65 degrees, it starts to feel humid and sticky. Above 70 degrees, most people feel very uncomfortable. Meteorologists use the dew point to help forecast weather.

Fun Facts

• Dew can provide water for small plants and insects in dry areas.
• The highest dew point ever recorded was about 95 degrees Fahrenheit in Saudi Arabia.
• Some beetles in the desert survive by collecting dew on their backs and letting it drip into their mouths.

Did You Know?

In some dry parts of the world, people use special nets to collect dew and fog as drinking water. A single fog net can collect several gallons of water in one night!