The 1976 heatwave featured 15 days over 32°C, but today's climate would push this to over 35°C.
Heatwaves are intensifying faster than average global temperatures, causing 3°C to 4°C rises in local peak heat.
Current UK infrastructure is built for a past climate and struggles to cope with modern extreme heat.
Projections suggest 45°C temperatures could become possible within three decades without significant emissions reduction.