The M5 was closed in both directions following a “serious collision” in the early hours of the morning, police said.
The motorway was shut at 02:00 GMT between J20 near Clevedon and J21 near Weston-super-Mare, according to Avon and Somerset Police.
Two lanes on the northbound carriageway have now reopened but the road is not expected to fully reopen until about 11:45 GMT, National Highways reports.
Elsewhere the M48 Severn Bridge is also closed in both directions due to strong winds, with the Met Office recording gusts of up to 45mph (72km/h).