Drivers on the A24 are facing long delays due to incidents including a car which rolled over.
One lane is blocked causing queuing traffic due to the crash southbound from Mill Straight to the A272 Cowfold Road, the AA said.
All traffic was held but it is now able to pass the collision, a spokesman added.
In a separate incident the A24 has been partially blocked after a tree fell onto a van just past Old Barn Garden Centre, according to traffic reports.
An AA spokesman said: “Slow traffic due to fallen tree on A24 Southbound at Worthing Road.”
“Not helped by the adverse weather conditions.”