Why were winter gritters out in Scotland during a heatwave?

Gritter lorries are normally sent out to melt snow and ice in winter, but in parts of Scotland during the heatwave, they have been used to help stop the roads themselves from melting!

The unusual move came as Scotland had its hottest day of the year so far, with temperatures reaching 31.2C in Threave, in Dumfries and Galloway just north of the border with England.

In the Scottish Borders, gritters spread a thin layer of sand over some main roads.

Gritters are usually used in winter to spread salt or grit, which helps stop roads becoming slippery when it is icy.

But in very hot weather, roads can have a different problem. Tar, which is the sticky black material used on road surfaces. It can soften when it gets extremely hot. This can damage the road and make it harder for vehicles to travel safely.

Scottish Borders Council said the B6362 Lauder to Stow road had to close because of heat damage, after road temperatures of 52C were recorded.

David Robertson, chief executive at Scottish Borders Council, said the council was not "being daft", but was trying to protect the road.

He said: "We're providing a fine layer of sand to prevent the melting of the tar," explaining that road temperatures above 40C was causing the tar to melt.

Gritter driver Alistair Fisher said: "We do get funny looks from people when they see us out and about gritting when it's so hot but it's needed to protect the roads."

A heatwave happens when temperatures stay higher than normal in an area for three days in a row. In Scotland, that means temperatures of 25C or more.

With thunderstorms on Thursday night through to Friday morning, the Met Office issuing a thunderstorm warning covering the whole country from midnight on Friday.