Special VFR

A clearance from ATC that lets a VFR flight enter, leave or fly inside a control zone (CTR) when the weather is below normal VFR minima. Under the European rules (SERA) you need at least 1,500 m visibility (800 m for helicopters), must stay clear of cloud and in sight of the surface, the ceiling must be at least 600 ft, and you fly at 140 kt or less.

You have to ask for it, e.g. “request special VFR to leave the control zone”, and ATC grants it only when traffic allows.