Parts of Britain are likely to be battered by a rare weather event as the latest weather maps have turned an unusual green.

Weather maps from WXCharts have turned bright green for some parts of Scotland, suggesting the falling of ice pellets on Saturday, November 23.

According to the Met Office, ice pellets are not the same as hail. Instead they are a type of solid precipitation that have a diameter of less than 5mm. They are spherical or irregular and rarely conical.

Ice pellets form 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 fall as snow pellets encased in a thin layer of solid ice.

The Met Office explained: “Ice pellets tend to be smaller than hailstones and bounce when they hit the ground. Like snow, they accumulate on the ground but form a smaller, denser covering which can be hard to clear away.

“They tend to occur in brief showers from tall cumulus clouds in the winter months.”

According to WXCharts, ice pellets are likely to fall on areas around Inverness, Wick and Aberdeen while other areas may experience heavy snowfall.

Jim Dale, a weather expert from British Weather Services, told Express.co.uk that having ice pellets in the UK is “quiet uncommon”.

He said: “Ice pellets are relatively uncommon.

“It is like essentially melting snow flakes falling through supercooled air (near the surface) – hitting the ground as small grains, a bit like polystyrene.

“Not as dangerous as hail but if enough falls it will blanket the surface akin to snow.”

The weather warning comes as the Met Office issued an amber alert for some parts of the UK on Saturday.

Storm Bert is predicted to reach the UK on Saturday, bringing heavy rain and snow, together with strong winds to large swathes of the country.

Met Office deputy chief meteorologist Dan Holley said: “Storm Bert marks a shift to much milder air and wintry hazards will gradually diminish through the weekend, but heavy snowfall is expected across parts of northern England and Scotland for a time on Saturday, especially over higher ground, and warnings are in place.

“Heavy rain through Saturday and Sunday, especially in southern and western parts of the UK, will also bring impacts for some with a number of warnings in place. We expect 50-75 mm of rainfall quite widely within the warning areas, but in excess of 100 mm is possible over high ground in parts of Wales and southwest England.”

He added: “In addition, rapid melting of lying snow over the weekend and periods of strong winds are likely to exacerbate impacts and bring the potential for travel disruption, as well as flooding for some.”