Dew is water in the form of droplets that appear on thin,exposed objects the morning or evening due to condensation.When the temperatures are low enough      dew takes the form of ice,this called as frost.

because dew is related to temperature of surface,in late summer it forms most easily on surfaces that are not warmed by conducted heat from deep ground,such as grass,leaves,railings,car,and bridges.

hope you like my answer