Significant roadworks started on the A31 from 20th September 2021.
An overview of the project and its impact can be seen here.
The best online information is given in the weekly view in the link below. This is released each Monday for the week ahead, so it is recommended that you check on the day. Whilst not always 100% correct, this has proven more accurate than other online sources.
You can also phone 0300 123 5000 which may give you the most up-to-date information.
Information about future weeks is given on the following link but has historically has not proven particularly accurate:
You can select the road (A31), direction and dates to look at.