What two important factors affect the formation of dew?

Relative humidity and temperature. Doug

humidity & temperature Though its a little more complicated than that .The amount of water vapor air can hold depends on temperature. The temperature at which air is saturated with water vapor is called the Dew Point. When surface temperature drops, eventually reaching the dew point, atmospheric water vapor condenses to form small droplets on the surface. This process distinguishes dew from those hydrometeors (meteorological occurrences of water) which are formed directly in air cooling to its dew point (typically around condensation nuclei) such as fog or clouds. The thermodynamic principles of formation, however, are virtually the same

The moisture & temperature of the air.

Humidity and temperature

temperature and humidity.

Dew occurs when water vapour in some quantity condenses on blades of grass, rocks or any warm surface close to the ground. It happens only in long winter nights, when temperatures are above 0 degrees celcius.