Gritters have been deployed as road temperatures reached 40c - causing them to melt.
Temperatures across Cambridgeshire peaked at 31c and concerns grew over the road surfacing material sticking to vehicles' wheels.
Agnes Owen, who works at a service station, said that it "sounded like cars were driving on water".
She said: "The tyres were literally ripping the tarmac off the road.
"It's quite dangerous!"
Fen Cops tweeted from the B1093, near Doddington, Norfolk saying "please be aware the road is melting, highways have been called, approach with care".
They also tweeted a picture of a gritter arriving to make the road safer.
Temperatures in much of Britain will continue to soar until at least Wednesday - as the country enjoys its longest continuous spell of high June temperatures since 1995.