Ice is simply water substance in a solid form. It occurs in the atmosphere and on the earth's surface and can take many different forms such as ice pellets, snow, hoar frost, rime, glaze and hail.

Ice can form over the surface of garden ponds, lakes and even rivers during exceptionally cold periods. It can also form over road surfaces, cars, building and vegetation in the form of black ice, frost or snow.

Glaze (clear ice)

Glaze is a smooth, transparent type of ice that forms when drizzle or rain hits a cold surface. It can either be formed when supercooled rain or drizzle comes into contact with the ground, or when non-supercooled liquid comes into contact within a surface that is well below 0 °C.

Due to its transparent nature glaze can often be mistaken for a wet surface and can be highly dangerous, particularly when driving. It can also be damaging when it gains sufficient thickness. The extra weight caused by the accumulation of glaze can bring down branches of trees and, on rarer occasions, telephone lines. It can also pose a serious hazard to ships by adding weight to the structure.

Black Ice

Glaze that forms on roads and pathways is often termed 'black ice' due to its transparent nature allowing the road surface below to be seen through it. Black ice is particularly dangerous since it can appear almost invisible to drivers. Find out more about driving in icy conditions.

Ice pellets

Ice pellets forms when snowflakes start to melt as they fall from the cloud, then fall through sub-freezing air, where they re-freeze into grain-like particles. Sometimes the snow may only partially melt and will fall as snow encased in a thin layer of ice.

Ice pellets are generally smaller than hailstones and bounce when they hit the ground. Showers of ice pellets tend to be quite short-lived, but can still accumulate on the ground in a similar way to snow though forming a smaller, denser covering.


Hail is a shower of round or irregularly shaped pieces of ice, known as hailstones. They originate as small ice particles or frozen raindrops that are caught in the updraught of air inside a cumulonimbus cloud. As they ascend, they gather water on their surface and grow. How large they grow depends upon how much water is in the cloud and how strong the updraught is.

Eventually the pieces of ice become so heavy that they can no longer be supported by the updraught and they fall to the ground.

Most hailstones are less than 25 mm in diameter, but they can grow up to 150 mm in diameter with potential to cause widespread damage to property and crops.

Other types of ice are covered across the learn about the weather section of the site. Use the links below to find out more about forms of ice in the UK, and being prepared for winter weather.

National Severe Weather Warning Service

Due to the risks associated with roads and pavements, ice forms one of the weather types for our National Severe Weather Warning Service. These warnings are issued to enable UK citizens to make informed decisions that help protect their life, welfare and property in the event of severe weather