So, jokes aside, to understand why the heat is worse in the UK than say Arizona for example, the answer is quite long... First it's the Humidity, it's far higher here. The UK's island location and prevailing south-westerly winds bring moist sea air, so heatwaves are often humid rather than dry. In contrast, many of the hottest US states (e.g., Arizona, Nevada, New Mexico) have dry desert heat where sweat evaporates quickly, so you actually feel cooler despite higher temperatures. Even humid US regions (like the Southeast) usually have widespread air conditioning to offset it. Second, the buildings and Infrastructure that we have all are designed to Trap Heat, not Release It. UK homes are built for cold, damp winters: thick brick/stone walls, heavy insulation, small windows, and designs that retain warmth. During a heatwave, they turn into ovens, solar gain through windows builds up, and there is poor ventilation or passive cooling features like overhangs, shutters, or light-coloured roofs. Plus, poor air conditioning: Only about 5% of UK homes have AC (vs. ~90% in the US). It's not standard because it's rarely needed most of the year, but during spikes it's a nightmare. Also, retrofitting is expensive and tricky in old terraced houses or listed buildings. This extended to public transport, schools, offices, and even hospitals as they often lack cooling. Finally, most importantly, we have zero acclimatisation. Meaning it's just as hot at night as it is during the day. Britons aren't physiologically or culturally used to sustained heat. We're properly white! So, a sudden jump from typical UK summer temps feels extreme, and the body struggles more without gradual adaptation. Heatwaves often bring "tropical nights" (temps staying above 20 °C), so homes don't cool down overnight. You can't sleep, recover, or anything which just compounds fatigue, dehydration, etc. Drier US heat often cools significantly at night. That is all topped up with the fact that we have longer summer daylight at the UK's higher latitude meaning more hours of solar heating. Hope this long explanation that no one wanted clears this right up...