What is a heat dome phenomenon that's left Europeans sweltering in the heat this summer?

England, France, Germany, Italy, and large parts of Europe are all experiencing a prolonged and severe heat wave that has left residents sweltering in the heat. This heat wave is not just a one-time event, but rather an ongoing phenomenon that has been affecting the region for several days, coinciding with the Northern Hemisphere's summer solstice. As temperatures soar to near-record highs, residents are being forced to take precautions to stay cool and safe.

The heat wave has been attributed to a mass of hot air moving north from the Sahara, driven by a solid high-pressure system called the 'African anticyclone.' This high-pressure system is creating a 'heat dome' that's trapping hot air over Western and Central Europe, resulting in temperatures that are climbing every single day. According to the Royal Meteorological Society (RMS), warming ground and increased moisture evaporation create conditions that allow temperatures to keep rising.

A heat dome forms when high pressure remains over the same area for several days or even weeks, trapping warm air underneath it like a lid clamped on a simmering pot. As the hot air expands, it forms a 'dome' that bulges outward. This phenomenon drives temperatures progressively higher during the day, often pushing them beyond seasonal averages since warm air becomes compressed over a smaller region.

The prolonged heat has been exacerbating the wildfire situation in several regions, with rescue centers taking in animals suffering from heat-related distress. In Germany, for example, heat warnings remain in place as temperatures have climbed to 38°C. Experts attribute the extreme heat waves to climate change, which is causing unpredictable and extreme weather to increase.

According to the World Health Organisation's (WHO) Europe office, above-average temperatures are expected again this summer, prompting emergency preparedness measures across Europe. European cities can better prepare for extreme heat by improving protection in residential buildings, installing shutters and fans, increasing funding for climate adaptation in public spaces, and creating emergency heatwave response plans.

The French transportation network has been severely disrupted by the extreme heat, with over 35 departments being placed on red alert. SNCF chief Jean Castex spoke at Paris' Gare Montparnasse station, highlighting the strong impact of rising temperatures on the rail network, which can destroy overhead power lines and expand railway tracks. In response, authorities have cancelled 71 intercity services on major routes until today.

Spain's weather agency, AEMET, has issued red and orange alerts across several regions, with temperatures forecast to reach 39–40°C in large parts of the Iberian Peninsula and Mallorca. The prolonged heat is causing chaos in several regions, with emergency services working around the clock to respond to the crisis.

In the UK, temperatures are expected to soar by up to 10°C above the seasonal average for mid-June. However, a varied and complex pattern is predicted, with northern and western parts experiencing rain due to cooler weather, while southern and eastern areas will heat up as temperatures rise.

The heat dome phenomenon is not a new occurrence, but its frequency and intensity are increasing due to climate change. As a result, European cities must prioritize climate adaptation and emergency preparedness measures to mitigate the effects of extreme heat events in the future.