Why this heatwave feels worse than the last one

Why this heatwave feels worse than – This week marks a significant moment as June temperature records are poised to be shattered, signaling the arrival of the second heatwave of the year in England and Wales. The air is expected to reach the mid- to high 30s Celsius, reminiscent of the conditions seen in May, creating a series of oppressively hot days and nights. Yet, for many residents, the discomfort of this wave may surpass that of the previous one, with perceived temperatures possibly exceeding the actual readings by several degrees. The combination of persistent high pressure, elevated humidity, and the arrival of tropical nights is intensifying the experience of heat, making it feel more extreme than the numbers suggest.

The Science Behind the Heat Dome

A high-pressure system, often referred to as a heat dome, is the primary driver of this intense weather pattern. According to Dr. Akshay Deoras, a senior research scientist at the University of Reading, such systems act as a trapping mechanism, preventing cooler air from entering and allowing heat to accumulate. When air descends under a heat dome, it compresses and warms, creating a feedback loop that sustains elevated temperatures. Additionally, the absence of clouds means the sun’s rays can directly heat the ground, further intensifying the thermal load. Unlike the May heatwave, which originated over the UK, the current dome is centered further east, over France, where temperatures have already reached into the 40s Celsius. This shift has allowed moist, warmer air to travel northward, significantly affecting the UK’s climate.

“This is not just a heatwave, it is a heat-dome driven furnace that will grip most of the southern UK and push temperatures into truly exceptional territory,” said Dr. Akshay Deoras.

The positioning of the heat dome plays a critical role in determining the severity of the heat. In May, the dome’s proximity to the UK meant the heat was concentrated locally, while now its presence over the sub-tropical regions has introduced a different dynamic. As the air mass moves, it carries with it a higher moisture content, contributing to the overall sensation of heat. This phenomenon is particularly notable in the UK, where the combination of humidity and heat has created conditions that feel more oppressive than the actual temperature metrics indicate.

Humidity Amplifies the Heat

Humidity is a key factor in making the current heatwave feel more extreme. While air temperature alone is a measure of heat, the moisture content in the atmosphere adds another layer of discomfort. When the air is humid, the evaporation of sweat from the skin is slowed, reducing the body’s natural ability to cool itself. During periods of high heat, this process becomes crucial for maintaining a stable internal temperature. Without effective evaporation, the body struggles to dissipate excess warmth, leading to a heightened perception of heat and increased risk of dehydration and heat-related illnesses.

The concept of “feels like” temperatures is used by meteorologists to account for these combined effects. For instance, if the air temperature is 35°C, the presence of high humidity might make it feel closer to 41°C. This discrepancy is not just a matter of perception; it reflects the real physiological strain on individuals. The body’s cooling mechanisms are less efficient in humid conditions, which means even moderate temperatures can lead to greater discomfort and health risks. This is especially concerning for vulnerable populations, such as the elderly or those with pre-existing medical conditions, who may find it harder to adapt to the prolonged heat.

Tropical Nights: A Hidden Threat

Overnight temperatures are also expected to remain elevated, with some locations failing to cool below 20°C. These are known as tropical nights, a term that highlights the unusual persistence of warmth. Thursday night may see the warmest June night on record, with minimum temperatures in Wales, the Midlands, and the South East likely to hover between 21 and 23°C. In fact, some areas could surpass the current UK and England records of 22.7°C and 20.3°C, respectively, which were set in 1976 and this week. The “feels like” temperatures during these nights could even reach 27°C, making the discomfort of the day seem to linger into the night.

Historically, heatwaves in the UK have been characterized by intermittent tropical nights, often occurring in isolated regions. However, the current event is different. The prolonged nature of the heat dome has created a scenario where multiple tropical nights may occur consecutively, leaving little opportunity for the body to recover. This continuous exposure can lead to cumulative heat stress, affecting both physical and mental well-being. Poor sleep, increased cardiovascular strain, and a greater likelihood of heat exhaustion are all potential consequences of this extended period of warmth.

Comparing the Current and Past Heatwaves

The comparison to the historic heatwave of July 2022 is apt, as both events have pushed temperature thresholds in the UK. However, the differences in humidity levels make the current situation more challenging. During the 2022 event, the air was notably dry, allowing the body to cool more effectively. In contrast, the present heatwave is marked by its moist conditions, which compound the effects of high temperatures. While the record-breaking 40°C temperatures in 2022 were impressive, the prolonged humidity of this June heatwave may lead to more significant health impacts, particularly for those who are less able to regulate their body temperatures.

As the planet continues to warm, heatwaves like this are becoming more frequent and severe. This trend suggests that the UK may experience similar or even more intense heat events in the coming years. The ability of the heat dome to trap and intensify heat, combined with rising humidity levels, points to a future where extreme weather is not just an occasional occurrence but a recurring challenge. Understanding these factors is essential for developing strategies to mitigate their effects, whether through personal measures like staying hydrated or systemic efforts to improve urban resilience to heat.

How to Stay Cool and Safe

While the heatwave poses challenges, there are practical steps to manage its impact. Keeping indoor spaces cool can be achieved through measures such as closing blinds, using fans, and ensuring proper ventilation. Hydration is also crucial, as the body loses more fluids in humid conditions. For those in high-risk groups, taking extra precautions during the hottest parts of the day is advisable. Schools and workplaces may need to consider flexible hours or breaks to reduce exposure. Despite the inconvenience, these measures can help alleviate the strain of prolonged heat and ensure that the population remains as comfortable and safe as possible.

The combination of record-breaking temperatures and persistent humidity is a stark reminder of the changing climate. As heatwaves become more frequent, the importance of understanding and adapting to their effects grows. The UK’s experience this June underscores the need for both individual preparedness and broader climate policies to address the increasing intensity of these events. Whether it’s the physical toll of high temperatures or the psychological stress of enduring prolonged heat, the impacts are clear. The question now is how well society will adapt to a future where such conditions are the norm.