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.
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The couple were driving from their wedding in Bristol to a hotel in Newquay when the snow hit.
Hundreds of schools have taken the decision not to open.
Heavy snow shut a 64-mile stretch of road between Exeter and Bodmin.