Extreme weather: heat

Status / emerging findings

• Scientific consensus is now irrefutable: likelihood of 40°C UK days has increased 40-fold from one-in-1,000 pre-industrial probability to one-in-25 years today, with further acceleration expected
• UK infrastructure built for cooler climates fails catastrophically at 40°C—railway tracks buckle, hospital lifts break, energy lines fail, water systems collapse
• Heat-related mortality declined in expected heatwaves but remains dangerously high during out-of-season events when populations are unprepared, indicating adaptation remains patchy
• Heat is a multi-system crisis affecting health, transport, water, energy and mental health simultaneously, with ageing housing stock and unprepared populations creating acute vulnerability

Why it matters

The UK has no coherent national strategy to prevent mass casualties and economic collapse during heat events now happening every few decades, not centuries.

Tone arc

Consistent urgency across both sessions; experts moved from establishing scientific certainty to stark description of infrastructure cascades and unequal geographic/demographic impacts.

Key witnesses

Professor Emma Howard Boyd CBE (National Heat Risk Commission chair), Professor Lea Berrang Ford (UK Health Security Agency Centre for Climate and Health Security), Professor Rowan Sutton (Met Office Hadley Centre director), Dr Richard Millar, Professor Swenja Surminski