Today’s Image of the Day from the European Space Agency features a Copernicus map of scorching summer temperatures across southern Europe.

“A powerful heatwave has been gripping large parts of southern Europe and North Africa, pushing air temperatures beyond seasonal norms and triggering widespread health and wildfire alerts. Among the hardest-hit countries are Spain, France, Italy, Greece, Cyprus, and Algeria,” said ESA.

“This image, a mosaic from five overlapping orbital passes in the morning of 29 June 2025, was captured by the Copernicus Sentinel-3 mission’s Sea and Land Surface Temperature Radiometer.” 

Tracking land surface temperatures 

According to ESA, the image reveals the temperature of the land surface – not air temperature.

Tracking land surface temperature is essential for predicting weather and climate patterns, assessing wildfire risk, helping farmers plan irrigation, and informing urban design strategies to reduce heat.

“Unlike measurements of air temperature, this satellite instrument measures the actual thermal energy emitted from Earth’s surface, which typically registers higher than air temperatures.”

Heat dome over Western Europe 

The image includes information from the Copernicus Marine Service, which shows that surface temperatures are also hot across the Mediterranean Sea.

The ongoing heatwave is fueled by a high-pressure system stalled over Western Europe, known as a “heat dome.” This system traps hot, dry air beneath it, causing temperatures to rise steadily. 

As it moves eastward, the dome pulls in even more hot air from North Africa, intensifying the extreme heat across the region.

Heat dome over the United States 

In June 2025, a heat dome developed over the central and eastern United States. It began forming around June 20 and persisted through the week.

The heat dome covered a large part of the country – from the Great Plains through the Midwest, Upper Midwest, Ohio and Tennessee River Valleys – and extended into the Mid‑Atlantic and Northeast regions.

More than 280 daily high-temperature records were shattered across the U.S., affecting some 130 million people under heat warnings or advisories. 

Cities like New York, Baltimore, Philadelphia, Boston, Newark, Providence, and Raleigh saw triple-digit highs – some reaching more than 105 degrees.

Public health concerns

The heat dome not only caused dangerous daytime highs but also oppressive night-time warmth, with low temperatures often staying above 80 °F due to trapped heat.

This persistent warmth strained power grids, led to emergency declarations, and triggered significant public health concerns.

Infrastructure suffered too: roads buckled in Missouri and softened asphalt sank vehicles in New York City, while a Baltimore Amtrak train stalled in a tunnel from the heat.

Emergency measures included power reductions, heat shelters, and utility advisories in several states.

Heat domes and climate change

Climate scientists emphasize that heat domes are fueled by anthropogenic climate change. These high-pressure patterns are occurring more frequently and enduring longer due to warming oceans, Arctic amplification, and altered jet stream behavior. 

As global temperatures rise, the atmosphere can hold more moisture and energy, which intensifies heatwaves and makes them more persistent. 

In particular, the weakened and meandering jet stream – a result of a warming Arctic – is allowing systems like heat domes to stall over regions for days or even weeks.

Adapting to a hotter future

Recent climate models show that events like the June 2025 heat dome (once considered rare), are becoming increasingly common. 

What used to be a one-in-100-year heat event in many U.S. cities may now occur once a decade or even more often. This shift has serious implications not just for human health, but also for infrastructure, agriculture, and energy systems. 

Power grids are pushed to their limits, roads and railways buckle under extreme heat, and crops suffer from both high temperatures and water stress.

Public health officials are especially concerned about the cumulative toll of prolonged extreme heat.

Nights that remain hot offer little relief and are particularly dangerous for vulnerable populations such as the elderly, young children, and people with chronic health conditions. 

Without sustained adaptation efforts – such as redesigning cities to reduce heat retention, expanding access to cooling centers, and modernizing energy infrastructure – the human and economic cost of extreme heat is expected to grow significantly in the coming decades.

Image Credit: ESA

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