Here's why:
* Water vapor in the air: The air around us always contains some water vapor, which is water in its gaseous state.
* Cooling surfaces: As the ground cools down at night, it cools the air immediately above it.
* Condensation: When the air cools to its dew point (the temperature at which it can no longer hold all of its water vapor), some of the water vapor in the air changes from a gas (water vapor) to a liquid (water droplets). These droplets form on the cool surfaces, like blades of grass, creating dew.
