The month-long Highways England scheme will tackle flooding issues on the section of the road near Whinfell Park, approximately 3 miles east of the town.
The majority of the work will be carried out overnight although a temporary 40mph speed limit will be in place at all times of day for the safety of drivers.
Peter Gee, Project Manager at Highways England, said:
The ditch next to the A66 is prone to becoming blocked which causes it to flood and leaves water on the road.
We’ll be installing a new drainage system which should prevent this from happening again in the future, but we’ll need to have a temporary speed limit in place so the work can be carried out safely.
The project will improve safety for drivers as it will reduce the risk of flooding on this stretch of road.
The majority of the work will be carried out overnight, between 8pm and 6am, with temporary traffic lights in use. Drivers may also be led through the roadworks in 10mph convoys on some occasions.
Members of the public should contact the Highways England customer contact centre on 0300 123 5000.
Journalists should contact the Highways England press office on 0844 693 1448 and use the menu to speak to the most appropriate press officer.