The A1066 in Diss reopened by 7pm last night after heavy rain caused flooding to close it.
The road was closed between the Scole roundabout and Sawmills Road, causing traffic chaos in the town, at about 3.30pm.
There was slow traffic in both directions between the A140 and the B1077 Stuston Road junction, while there were tailbacks on Mere Street and Chapel Street.
South Norfolk Police had advised motorists to use alternative routes.
A spokesperson for Norfolk County Council told the Diss Express last night: “Reports of flooding on the A1066 have been passed to our out of hours highways team and they will be checking the situation.
“Sustained or intense periods of heavy rainfall and thunderstorms can cause roads to get suddenly inundated and we’d ask road users to please take extra care in the area during these conditions.”