Question

How Dew is formed on grasses at night??

Answer 1

Since at nights are cold, the moisture absorbed during the day will condense and will be seen as dew drops on flowers, leaves, grasses

Answer 2

As known to everybody nights are cold. The moisture content present in the air is called humidity. The water vapour present in the air cools down in the night's chillness. The cooled water vapour settle down on the leaves and grasses forming dew.
Hope this helps: )