The United Kingdom is currently experiencing a heatwave characterized by unusually high overnight temperatures and increased humidity, making it feel more intense and potentially more dangerous than previous hot spells. Overnight lows in some areas are not expected to dip below 20C, a phenomenon known as "tropical nights."
This week could see the warmest June night on record, with minimum temperatures across Wales, the Midlands, and the South East forecast to remain between 21C and 23C. These temperatures could surpass the current UK and England record of 22.7C, set in 1976, and the Wales record of 20.3C, which was set earlier this week. The perceived temperature, or "feels like" temperature, may reach as high as 27C during the coolest parts of the night.
A key distinction from previous heatwaves, such as the one in July 2022, is the duration of these tropical nights. While the 2022 heatwave saw many areas experience tropical nights, few had more than two consecutively. This current event may see some locations endure three or four consecutive tropical nights. This sustained warmth prevents the body from cooling down sufficiently between periods of high daytime heat, increasing the risk of heat-related illnesses.
The prolonged and intense heat poses significant risks not only to vulnerable populations but also to healthy individuals. It can lead to poor sleep, cardiovascular stress, and an elevated risk of heat exhaustion in the days that follow.
Experts attribute the increasing frequency and intensity of such heatwaves to global warming, driven by the emission of greenhouse gases. A warmer atmosphere holds more moisture, and this combination of higher temperatures and increased humidity creates more potent and frequent humid heatwaves. Without substantial reductions in greenhouse gas emissions, these conditions are expected to worsen and accelerate.