The A285 in Duncton, near Petworth, is closed for emergency repairs.
The high street is reportedly closed both ways after the road collapsed during heavy recent rainfall.
"Please find [an] alternative route," wrote Sussex Roads Police officer Pete May on Twitter.
Police in Crawley have been called to Steers Lane in Pound Hill after a missing manhole cover was reported. Pictures on social media show a potentially dangerous hole in the road.
Residents on social media have also reported severe flooding in Cripplegate Lane, Horsham. A stuck car was pictured at the bridge on Saturday evening.
Meanwhile, some lines are closed on the railway today due to engineering works between Brighton and Lewes.
This means that throughout the day, rail replacement buses will operate. However, from 3pm until the close of service, a very limited bus service will run.