Under what conditions does frost typically form?

Frost formation occurs under specific atmospheric and temperature conditions. The correct answer highlights that frost typically forms when both the collection surface (such as grass or a car windshield) and the dew point are below freezing, accompanied by high humidity.

This combination is crucial because frost forms when the temperature of the surface falls below the freezing point of water, allowing water vapor in the air to condense directly into ice crystals instead of first becoming liquid water. High humidity indicates that there is enough moisture in the air, which is necessary for frost to develop. When the dew point is also below freezing, it reinforces that the air is cold enough to support frost formation, as the dew point represents the temperature at which air becomes saturated with moisture.

In contrast, if the dew point is above freezing or if humidity is low, the conditions are not conducive to frost formation because there won't be sufficient moisture in the air to condense as ice crystals. Similarly, warm and humid conditions would not lead to frost but instead could result in other types of precipitation. Therefore, the conditions outlined in the correct answer are essential for understanding frost formation in meteorology.