In an explainer on its website, National Highways says it shuts M48 Severn Bridge to all traffic when they expect gusts above 40 knots (46mph).
It then remains closed “until wind speeds have dropped”.
If wind speeds exceed 70 knots (80mph), they also close the nearby M4 Prince of Wales Bridge.
“Traffic can still travel between England and Wales by following a diversion using the M5, M50, A40 and A449,” the agency says.
National Highways says their traffic officers “previously filtered vulnerable westbound traffic (lorries, motorbikes, and high-sided vehicles) during high winds”.
“This involved fewer full closures of the bridge. However, it meant that traffic officers had to physically filter vulnerable vehicles on site to stop them travelling on the bridge.
“Working in high wind, as well as poor weather and low visibility, became increasingly hazardous for our teams.
“This is why we decided on safety grounds to stop filtering high sided vehicles and motorcycles during high winds.”