The A55 between Junction 11 at Bangor and Junction 12 Tal y Bont has been partially reopened in both directions.
It had been closed due to floodwater, with rest centres for stranded drivers opened at Caernarfon, Bangor and Llandudno Junction.
– Chief Inspector Alex Goss, North Wales Police
A further detailed examination of the road will take place in daylight when all agencies will concentrate efforts on fully reopening the A55. Until such time a temporary speed limit of 40 MPH will be in place. Although weather conditions and the traffic back log have improved we are still advising motorists to journey out only where necessary and check first with Traffic Wales, local radio or TV and take extra care as roads will still be very wet.