The photos taken on Tuesday morning appear to show a phenomenon called a temperature inversion.
Remarkable aerial photos have been released showing a blanket of fog covering the Severn crossing.
The images, taken by National Police Air Service helicopter on Tuesday morning, appear to show a phenomenon called a temperature inversion.
This happens when a layer of air sinks towards the ground, drying and warming as it goes.
This creates a warm layer of air that acts as a “lid” and traps cooler air near the surface, according to the Met Office.
After the pictures were posted by the NPAS South West Twitter account, one motorist responded: “This was surreal, especially driving through it.”
Further images captured by Highways England cameras showed the bridge – which carries the M4 motorway between England and Wales – submerged in mist.
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