Frost to the ground is night frost
Night Frost (or frost to the ground) is when the temperature drops just above the ground to below freezing. Normally the temperature on weather stations is measured at about 1.5 meters above the ground, the temperature just above the ground may be different. Frost to the ground freezes the water vapor, the frozen droplets are often seen as a white attack (ripe). In winter, night frosts occur about half of the days.