May 2026 was the hottest month ever. A heat wave like this had never been seen before, especially in Europe, where 11 deaths have already been recorded and temperatures are expected to rise sharply throughout the summer.
The record was set in London, where temperatures rose to 35 degrees in May 2026 (the previous year, in the same month, they were around 32 degrees). In Italy, the heat is very abnormal, especially in central and northern Italy, with peaks of 35–37°C already in May: a full 5 degrees above average. In Turin, the thermometer reached 33 degrees in May, in Rome and Bologna 31 degrees, and in Florence 30 degrees.
Meanwhile, the Barcelona Institute for Global Health announced that 180 deaths from excessive heat in 32 European countries between 2022 and 2024.
The main causes of the exceptional heat this May are a combination of factors attributable to the climate crisis, in turn fueled by the failure to reduce greenhouse gas emissions.
Very intense subtropical anticyclone
In recent weeks, a strong anticyclone of North African origin, often called a “subtropical anticyclone”, has expanded over southern and western Europe.
This involves:
- very hot air coming from the Sahara;
- clear skies and strong solar radiation;
- absence of Atlantic disturbances;
- compressing the air downwards, which further increases temperatures.
In practice, the atmosphere remains “blocked” and the heat accumulates day after day.
Exceptionally warm seas
The Mediterranean Sea and parts of the eastern Atlantic have above-average surface temperatures.
The warm sea:
- transfers more energy and moisture to the atmosphere;
- makes already warm air masses even more unstable and muggy;
- reduces nighttime cooling.
In recent years, the Mediterranean has been warming much faster than the global average.
Climate change
The underlying factor is global warming caused mainly by greenhouse gas emissions.
The main effects are:
- increase in average temperature;
- more frequent heat waves;
- longer and more intense extreme events;
- heat records broken most often.
Scientists explain that phenomena like this are not “created” by climate change, but are made:
- more likely;
- more intense;
- more persistent.
It's a bit like "loading the dice" of the climate system.
Jet stream more wavy
Some climatologists also link these atmospheric blockages to changes in the jet stream.
When the jet stream slows down or becomes very wavy:
- atmospheric configurations remain stable for longer;
- heat and drought persist for weeks.
It's one of the reasons why we see longer extreme periods more often today.
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