An introduction to how frost forms and why it can be difficult to forecast.
Frost is normally formed on still, clear and cold nights. The cool air causes water vapour in the air to condense and form droplets on the ground. When the temperature of the ground or surface is below 0 °C the moisture freezes into ice crystals - known as the frost point.
Find out more about different types of frost and the challenges involved in forecasting it in the articles below.