The Met Office has issued a red extreme heat warning for parts of England and Wales, warning that an exceptional spell of hot and humid weather could bring serious health risks and major disruption.

The warning runs from 09:00 on Wednesday 24 June to 21:00 on Thursday 25 June. The Met Office says maximum temperatures in the shaded area are increasingly likely to exceed 37C, perhaps reaching 38C to 40C in some places.

That updates earlier reporting based on amber warnings. The latest Met Office warning map shows red warnings for Wednesday and Thursday, with amber warnings in place before then.

The UK Health Security Agency has also issued red heat-health alerts for six English regions: East of England, East Midlands, London, South East, South West and West Midlands.

The warning is serious because the expected impacts are not limited to vulnerable groups. The Met Office says population-wide adverse health effects, disruption to working routines, pressure on heat-sensitive systems and transport delays are likely.

The event also raises a wider adaptation question. Extreme heat is no longer only a Mediterranean issue; UK homes, transport networks, schools and hospitals are increasingly being tested by conditions for which much of the country was not designed.