Heatwave: Why It Feels Hotter Than It Is

The Heat Dome Effect

The UK and parts of Europe are bracing for a scorcher of a week as a heat dome, a large area of high pressure, settles in, bringing record-breaking temperatures. This phenomenon, explained by Dr. Akshay Deoras, a senior research scientist at the University of Reading, is the driving force behind the intense heatwave.

The heat dome causes air to sink and warm up as it moves through the atmosphere, resulting in drier conditions and more sunshine heating the ground.

This week’s heatwave has its origins in the sub-tropics, with the heat dome centred over France, where temperatures have already soared into the 40s Celsius.

The Role of Humidity

But it’s not just the heat that’s making headlines. The humidity is a key factor in why this heatwave feels worse than the last.

Humidity measures the moisture in the air, and during hot weather, our bodies regulate temperature by sweating. When the air is humid, sweat doesn’t evaporate as easily, making it harder to cool down.

Meteorologists can calculate a “feels like” temperature, which combines air temperature and humidity. So, while the thermometer might read 35°C, it could feel more like a sweltering 41°C.

Comparing Heatwaves

The current heatwave is drawing comparisons to the historic July 2022 event when the UK recorded its first-ever 40°C temperature. However, the air was much drier then, making this June’s heatwave feel hotter despite slightly lower headline temperatures.

This difference in humidity can have significant health impacts, as the body struggles to cool down effectively.

Tropical Nights and Health Risks

Overnight temperatures will also remain high, with some areas not dropping below 20°C, known as “tropical nights.” This week could see the warmest June night on record, with “feels like” temperatures making it feel like 27°C even during the coolest parts of the night.

This is a notable shift from previous heatwaves, where tropical nights were less common and rarely consecutive. The consecutive tropical nights in this heatwave mean the body has less chance to cool down, increasing health risks, especially for vulnerable individuals.

As the world warms, heatwaves like these will become more frequent and intense, according to Dr. Deoras. The combination of increased temperatures and humidity is a major concern, highlighting the need for adaptation and resilience strategies.

So, while the heatwave may feel unbearable at times, understanding the science behind it can help us prepare and adapt to these increasingly common weather events.