A spokeswoman for South Western Ambulance Service said the boy hit by an ambulance in Bath is now in a "stable condition".
"He was transferred to Frenchay Hospital because he is suffering from head trauma and the hospital has a specialist major trauma unit," she added.
More top news
Downpours keeping us on our toes today
The M20 in Kent has been closed in both directions after a pedestrian bridge allegedly collapsed on the motorway on Saturday.
The AA have warned of traffic jams and urged people to carry extra water in their vehicles because of the warm weather.