Children and babies are more vulnerable in heatwaves than healthy adults. As temperatures rise again, how do we keep children safe? Why are children more vulnerable to hot weather? The biological systems that regulate heat in the human body are controlled by a region of the brain called the hypothalamus. It is the body’s master thermostat, acting to keep our internal temperature around 37C. It also detects when we need more fluids. When the hypothalamus detects a rise in temperature, it initiates responses such as sweating, which cools the body through evaporation, or vasodilation, which directs warm blood to vessels near the surface of the skin, where heat can radiate away. But in children, particularly those under the age of five, the hypothalamus is not fully developed. They sweat less and do not realise when they are thirsty. Also, children’s smaller physical size gives them a substantially greater body surface area-to-mass ratio than adults, meaning they absorb heat faster. They are also more likely to be physically active, and less likely to pace themselves, giving …