The A35 was closed this morning between the Stadium Roundabout in Dorchester to the Stinsford Roundabout.
It was closed around 1am as heavy rain fell overnight flooding the road with Storm Chandra causing disruption in Dorset.
Traffic was reported to be heavy on the approach to Stadium Roundabout in all other directions with delays expected to be longer during peak times.
An amber weather warning was in place until 9am this morning.