Europe’s heat dome explained: Why the continent is boiling under extreme temperatures

Dubai: A fierce heatwave is scorching much of Western Europe, with temperatures breaching 40°C in Spain, sparking wildfires in France, and prompting red alerts across the continent.

Paris is bracing for highs of 40°C, while Belgium, the Netherlands, Germany, and the UK endure sweltering days with little relief.

In Seville, where the mercury hit 42°C, UN Secretary-General António Guterres warned: “Extreme heat is no longer a rare event — it has become the new normal.”

Scientists say a “heat dome” is to blame — a powerful high-pressure system that traps hot air and blocks cooling.

With climate change driving more frequent and intense heatwaves, the health risks are soaring, especially for the elderly, children, and those with chronic illnesses.

So, what exactly is a heat dome? How does it work, and why is it becoming more common? Here’s a detailed explainer on this dangerous weather phenomenon reshaping summers worldwide.

A heat dome forms when a large area of high pressure stalls in the upper atmosphere, trapping hot air underneath like a lid on a pot, National Geographic says. This prevents heat from escaping and blocks the formation of clouds, resulting in relentlessly sunny skies and rising temperatures.

The trapped air compresses and heats up as it sinks, creating a “dome” of intense heat near the surface. This system often spans hundreds of miles and can persist for days or even weeks.

The longer it stays in place, the more heat builds up — dark surfaces like asphalt and rooftops absorb and radiate more heat, soil dries out, and wildfire risks increase. Relief only comes when another system, such as a storm or low-pressure front, pushes the dome away.

Heat domes aren’t random — they’re caused by disruptions in the atmosphere, particularly in the jet stream, a fast-flowing band of wind high above the Earth. When the jet stream becomes wavy and sluggish, it can trap high-pressure systems in place, giving rise to a heat dome.

Ocean patterns like La Niña can also contribute by warming sea surface temperatures and altering air flow. These changes help establish the conditions necessary for a heat dome to form — dry, cloudless weather and prolonged sunshine.

In short, it’s the combination of blocked air circulation, trapped heat, and dry land conditions that allows a dome to intensify and linger.

Unfortunately, heat domes tend to be stubborn. They move slowly, if at all, and can squat over entire regions for extended periods. Their path and duration depend largely on the behaviour of the jet stream, the magazine says.

When the jet stream weakens or shifts, the dome can expand or drift into new areas. Only when the high-pressure ridge breaks down does the heat dome dissipate — usually triggered by the arrival of cooler air or storm systems.

According to the IPCC Climate Change 2023 Synthesis Report, it is virtually certain that extreme heat events have become more frequent and intense across most regions since the 1950s.

Climate change intensifies heat domes in several ways:

Baseline temperatures are higher due to global warming, so heat domes start from an already warm state and become hotter.

Soil moisture levels are lower, meaning less evaporation and cooling.

Jet stream behavior is changing, possibly linked to Arctic warming, which causes more stagnant air patterns that allow heat domes to linger longer.

Simply put, heat domes are becoming hotter, more frequent, and longer-lasting — and climate change is a major driver.

Extreme heat, especially when combined with humidity, puts serious strain on the human body. Our primary cooling system — sweat — becomes less effective when the air is already full of moisture. This reduces the body’s ability to cool itself through evaporation.

As a result, core body temperature rises, leading to:

Dehydration

Heat exhaustion

Heatstroke — which can be life-threatening

At greatest risk are older adults, young children, people with chronic health conditions, and outdoor workers. According to the EPA, extreme heat already causes more than 1,300 deaths annually in the US alone.

To protect yourself during extreme heat:

Stay hydrated: Drink plenty of water.

Avoid going out during peak heat hours (usually 12–4 PM).

Seek cool environments: Use air conditioning, fans, or cooling centers.

Use creative cooling methods: Take cold showers, soak feet or arms in cold water, or sit in front of a fan with a cool cloth on your skin.

If air conditioning isn’t available at home, make a heat plan: locate nearby malls, libraries, or community cooling centers, and check on vulnerable friends and neighbors.

Watch for signs of heat stroke — such as confusion, dizziness, and rapid heartbeat — and seek medical help immediately if symptoms appear.

Yes. Not only are heat domes happening more frequently, but they’re also arriving earlier in the year and lasting longer. Europe, which is warming at twice the global average, is already seeing more intense heat events — and the summer outlook for July–September shows a high likelihood of above-average temperatures.

While each individual heat dome requires a specific attribution study to confirm the role of climate change, scientists say the trend aligns with warming projections. Spain has likely just recorded its hottest June on record, while Portugal saw a record 46.6°C in one southeastern town.

With global temperatures already up nearly 1.3°C since the Industrial Revolution, experts warn that unless emissions are curbed, events like this will become even more extreme.