Most of England and Wales face a fierce heatwave in the next few days, with parts of southern England set to come close to 40°C. While the UK has reached this point before, there’s a special feature of this heatwave that will make it feel worse than ever – the humidity.
Humidity – the amount of water vapour being carried in the air – is important because high levels interfere with sweating, the main way that that we cool down. So, when it is both hot and humid, it feels warmer than the air temperature suggests.
“When humidity is high, sweat cannot evaporate as effectively, so the body struggles to regulate its temperature even if the air temperature itself is not at its peak,” says Professor Hannah Cloke, a climate expert at the University of Reading.
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This means that not only will it feel muggy and unpleasant, but people may also be at higher risk of suffering serious health consequences.
