Dew is liquid water droplets that form on grass, spider webs, and other things in the early morning or late evening. Dew only forms under certain conditions. If a warm, clear day is followed by a cool, clear evening,dew will likely form. On a normal warm day, water evaporates from the warm ground into the air. Dew is made of liquid water that has condensed from some of the water vapor in the air. Dew occurs when objects cool. Dew forms when the object, such as the grass, cools down to the dew point temperature. Water molecules in the air continually bombard surfaces, like blades of grass.

https://wonderopolis.org/wonder/why-is-the-grass-wet-in-the-morning