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.

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. As the instrument’s name suggests, the image reveals the temperature of the land surface, not air temperature. 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. Click on 'download' (above) for the 'hi-res' annotated image.

It's not just the surface of the land that’s hot, so too is the sea surface of the Mediterranean Sea – as the image also shows using information from the Copernicus Marine Service.

Monitoring land-surface temperature is crucial for understanding and forecasting weather and climate patterns, tracking wildfire risks, supporting farmers with irrigation planning, and guiding urban design to better mitigate heat.

The current heatwave is being driven by a high-pressure system stalled over Western Europe, commonly referred to as a ‘heat dome’. This system acts like a lid, trapping hot, dry air and amplifying temperatures over time. As it shifts eastward, it is also drawing in additional hot air from North Africa, further exacerbating the extreme heat across the region.