The controversial Broadbridge Heath bypass works could over run until after Christmas, the council said.
In a statement, West Sussex County Council said some areas may need finishing off after Christmas after the bad weather had delayed works.
The works, which involved closing the A281 before downgrading it so only buses and taxis can use it, have sparked a huge public backlash.
A council spokesman said: “The majority of the project is planned to be completed in late autumn (at the end of November/early December), particularly for the Billingshurst Road/connector road opening.
“Like all construction projects, this is subject to unknown factors, such as severe weather.
“The recent poor weather has had some impact on the project’s timetable and it is possible there could be areas to finish off after Christmas.”
But the work would be a ‘relatively minimal amount’ at Farthings Hill and the Newbridge roundabout, he added.
The spokesman said: “The scheme involves the permanent closure of a section of the A281, which went through the middle of the village, and building improved links between ‘old’ and new housing areas. Improvements also include new shared-use cycle and pedestrian paths.”