The scheme will see a full programme of maintenance works, including carriageway resurfacing and footway and kerbing works, starting on 9 January for 31 days until Friday 17 February.
A diversion route will be in place during the six-phase schedule. Full details can be found on One Network website at https://one.network/?GB131918256.
During phases one and three, there will be temporary two-way lights. Roads affected are Nore Road, Coombe Avenue, West Hill Gardens, Avon Way and Down Road.
Throughout the remaining phases daytime road closures will be in place between the hours of 8am and 5pm.
A night closure will be required towards the end of the scheme (16 to 17 February) so crews can work safely to carry out lining and drainage works.
No works will be carried out during the weekends.
Cllr Steve Hogg, North Somerset Council's Executive Member for Transport and Highways, said: “This investment in the highway asset will provide an improved, safer road surface for motorists and prolong the life of the road by protecting it from environmental damage.
“We appreciate that a night closure on a busy route will cause some inconvenience, but we carry out works overnight when traffic volumes are lower, to minimise disruption and avoid peak travel times.”
Cllr Nicola Holland, North Somerset Council's ward member for Portishead West, said: "Portishead residents are very pleased to see work finally start on this very old and very important road, which has unfortunately been neglected for too long.
"The topography of our town and the history of the road network here means that this narrow, windy hill is actually one of the main links between the north and south and so it is extremely important that it is maintained properly."
You can find the latest information and regular updates on the North Somerset Travel and Roads social media pages: https://twitter.com/NStravel_roads on Twitter and https://www.facebook.com/NStravelandroads/ on Facebook.