An exceptional heatwave is affecting countries across western Europe, with cities and regions of France, Spain and southern Italy experiencing unseasonal temperatures.

This image of land surface temperature was captured by the Copernicus Sentinel-3 mission on Wednesday, 23 June. The data were captured in the late morning, local time.

You can watch a video about this image here.

The colours shown on the image range from purples and deep reds (indicating surface temperatures up to 55ºC, seen in parts of central Spain, western France and northern Africa) to light blues that indicate lower surface temperatures in mountainous regions. Some areas were covered by cloud – shown in white.

The satellite sensed temperatures on land of 48ºC in Madrid, 44ºC in Rome and 46ºC in both Poitiers in France and Zaragoza in Spain. The ground temperatures in northern Africa are visibly higher, with temperatures on the ground in Tunis reaching 49ºC. Because surfaces such as rock, sand and asphalt retain the heat, ground temperatures are considerably higher than air temperatures.

Sentinel-3 carries four instruments, including its Sea and Land Surface Temperature Radiometer (SLSTR) – a powerful and highly accurate sensor that measures temperatures over both land and sea. It detects heat stress over land and its data are used in agriculture as well as monitoring urban heat islands and wildfires.

The current European heatwave is caused by an atmospheric pattern of persistent high pressure – a ‘heat dome’ – which is trapped over Europe between low pressure systems on each side. Summer heat in Europe is not normally associated with El Niño and therefore, although satellite data have detected early signs of the El Niño phenomenon in the Pacific Ocean, it is not the driver behind the current temperatures in Europe.