Ramanath Parimi

Dew on grass will from only under certain weather conditions, that too on early morning or late evening.

Weather consists of humidity, along with many elements. Humidity is nothing but water moisture. This is the reason for presence of precipitation, fog and dew in the weather.

This moisture turns into air when temperatures are warm (We call this water vapour and this process is called evaporation), and turns into water when temperatures are low(We call this dew and this process is called condensation) .

Now let us understand the weather differences between day and night.

If a warm day gets followed by a cool weather (be it early morning or late night), dew will have more chances of formation. In the mid-day normally, the water evaporates from the warm ground and goes into the air.

As the night starts and progresses, the temperature of the weather becomes cold. The warmer ground still continues to radiate heat into the air but at this point, the ground also begins to cool. As this happens, the air above will not be able to hold all the moisture.

At a certain point, called as dew point, the water vapour in the air starts to condense itself. Meaning, it turns back to liquid water faster than it turns itself into vapour. As this happens, we see dew forming on the surfaces which aren't effected by the warmth radiated from the ground, like grass, leaves and car roofs.