Andy Osira 🇺🇦

38°C in Britain is more dangerous than 45°C in Phoenix, and it comes down to one number: your body sits at 37. Once the air outside is hotter than your skin (around 35°C), heat stops flowing out of you. Radiation and convection reverse. The air starts heating you instead. At that point your body has exactly one cooling system left: sweat turning to vapor and pulling heat off your skin. Phoenix is built to protect that system. Around 90% of US homes have AC, the air is bone dry so sweat evaporates the instant it forms, and the whole city is designed around triple digits. Britain is built to defeat it. Roughly 5% of homes have air conditioning. About 92% overheat during a heatwave. Half the housing stock went up between 1930 and 1982, with thick walls and small windows meant to trap warmth through a damp winter. The same features that keep a house cozy in February turn it into an oven that won't release heat in July. Then the sun goes down and nothing changes. A real heatwave brings tropical nights where the temperature never drops below 20°C. Your body resets by dumping the day's heat overnight. Remove that recovery window and the strain stacks, night after night. That's why London's heat death rate rivals Rome's, and why the UK loses more than ten times as many people to heat as Sweden does. The 2022 heatwave killed around 3,000. At one point the Central Line was running hotter than the legal limit for transporting cattle. Phoenix planned for the heat. Britain assumed it would never arrive. 38 stays a small number right up until it's one degree above the one inside you.