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Wet Bulb Effect: Why This UK Heatwave Is So Intense
25 Jun
Summary
- High humidity, not just temperature, intensifies the current heatwave.
- Wet bulb effect occurs when humidity prevents natural body cooling.
- This heatwave poses severe health risks like heatstroke and dehydration.
The current UK heatwave's intensity is attributed to significantly higher humidity levels, making it feel worse than previous hot spells. Meteorologists explain this through the 'wet bulb' effect, where increased moisture in the air prevents sweat evaporation, thus inhibiting the body's natural cooling mechanisms.
Professor Hannah Cloke highlighted that current conditions, with around 30C and 50% humidity, create a higher wet bulb reading compared to the drier conditions during the 2022 heatwave. This means the body must work harder to cope, even if air temperatures are slightly lower. The combination of heat and humidity is crucial, not just the thermometer reading.
The Met Office warns that high humidity poses serious health risks, including heat stress and dehydration. In severe cases, heatstroke or cardiovascular complications can occur, with the elderly, children, and those with pre-existing conditions being particularly vulnerable. Forecasters suggest the 'heat index', a combination of temperature and humidity, could make it feel up to 10C hotter than the actual air temperature.
