Daily minimum temperatures are forecast to remain above 20°C in many parts of Europe over several days during the heatwave. Why do “tropical nights” need attention? Night time is when the body is supposed to recover from daytime heat. When we sleep, our core temperature drops, our cardiovascular system rests, and the cumulative stress of a hot day begins to ease. When nights stay warm, that recovery does not happen. The body remains under strain around the clock. When assessing the health impact of a heatwave, minimum temperatures can be more telling than the peak afternoon high. A day that reaches 38°C but drops to 18°C overnight is very different from a day that reaches 36°C and stays above 25°C through the night. The second scenario carries a much higher health risk. Prolonged exposure to heat, particularly when temperatures remain high at night, means the body enters each new day already stressed. Older adults, young children, pregnant women, outdoor workers and people unhoused...