Gritters out as Scotland braced for 30C on hottest day of the year

David Robertson, chief executive at Scottish Borders Council, said they were expecting temperatures to reach 31C in Newcastleton and Hawick.

He said: "If you see the gritters, it's not the council being daft, it's us actually trying to protect the road surface.

"We're providing a fine layer of sand to prevent the melting of the tar.

"What we're seeing is ambient road temperatures at the height of the heat up in the 40s, and that causes the tar on the roads to melt."

Meanwhile, Dumfries and Galloway Council has asked residents to "spare a thought for our frontline staff" wearing personal protective equipment in the heat.

Police Scotland issued reminders about water safety and the risk of drowning, external from "cold water shock".

However, anglers in the south have been warned about the risks to fish when rivers warm up.

The River Tweed Commission (RTC) called for a stop to fishing salmon and trout when water temperatures reach 20C, external because dissolved oxygen levels puts fish under stress, meaning even careful catch-and-release angling can kill them.

Jamie Stewart, from the River Tweed Commission, said: "Wild Atlantic salmon are already facing unprecedented pressures from climate change, habitat loss and poor marine survival."

BBC Scotland weather presenter Gillian Smart said the heat would peak as southeasterly winds pull in intensely hot, humid air from the continent.

She said: "The highest temperatures will be in central and southern Scotland, where we're likely to see 30 Celsius."

However, she warned of a "thundery breakdown" on Thursday afternoon.

"A weather front to the northwest will interact with the very warm air to produce heavy, thundery showers across the Western Isles, the Northwest Highlands and the Northern Isles.

"These thundery showers will feed southwards across the country, torrential in places, and bringing a risk of hail."

A yellow warning for thunderstorms has been issued for Highlands, Orkney, Moray and Argyll and Bute from 15:00 to 23:59, and for the rest of mainland Scotland from 00:00 to 23:59 on Friday.

Parts of England and Wales have a rare red warning for extreme heat in place and it is expected to be another scorching day for most of Europe.

Temperatures will once again be around 12 to 15C above average across northern Spain, France and into Belgium and the Netherlands.