Summary:
- Humidity is the amount of water vapor in the air.
- Warm air can hold more water vapor than cool air.
- The heat index is a measure of what the temperature feels like because of the humidity.
- Water droplets form when the air reaches 100% humidity.
- If the temperature is cold enough, frost will form on the surface of the grass.
- If this temperature is below freezing, ice crystals of frost form instead of dew (Figure below).
- The dew point occurs at 100 percent relative humidity.