Severe thunderstorms hit France, Germany, and Poland on July 17, 2026, as the worst heatwave ever recorded in Europe kept shaking up the weather across the region (The Guardian).

In south-eastern France, hailstones as large as 5 to 7 centimetres — about the size of a tennis ball — fell on the towns of Aubenas, Vals-les-Bains, and Lalevade-d'Ardèche in the Ardèche area on July 15. The hail broke car windscreens, damaged buildings, and destroyed parts of vineyards. Météo-France, the country's national weather service, confirmed hail bigger than 5 centimetres in Isère (department 38) in a bulletin issued at 06:00 on July 17. That same day, the agency's weather warning map showed an orange alert — the second-highest level — for thunderstorms, specifically mentioning 5-centimetre hail.

Météo-France had been raising its warnings for days before. On July 15 at 16:02 Paris time, it issued orange thunderstorm alerts for three areas: Eure (27), Ille-et-Vilaine (35), and Mayenne (53). The Loire department (42) got its own alert starting at 22:00, warning of violent storms likely to cause significant local damage. Puy-de-Dôme (63) was flagged for organized storm activity with strong winds and large hail. Rainfall of 30 to 50 millimetres was expected across France, with some areas possibly getting more.

In Poland, the main problem was flooding. In the south-western city of Wrocław, floodwater closed roads and tram tracks, and strong winds knocked trees onto tram power lines. Poland's weather service, IMGW-PIB, had seen this coming: its weekly forecast for July 13–19 warned that thunderstorms could be violent in places, with heavy rain causing flooding. An earlier forecast for July 10–12 had predicted scattered storms with up to 25 millimetres of rain in the northeast and top temperatures starting from 18°C. IMGW-PIB's seasonal outlook had already warned that July 2026 "would not be an ordinary summer," blaming warmer, more humid air flowing in from the Atlantic.

These storms are part of a heatwave that started on June 20, 2026. Reuters reported on June 26 that scientists called it the worst European heatwave on record (Reuters). The Associated Press confirmed record temperatures in Switzerland, the Czech Republic, and Denmark (AP). The heat killed dozens of people as it spread eastward across the continent, according to a Reuters report dated June 27. Power cuts in France on June 24 left thousands of people without air conditioning or cooling during the hottest part of the day.

The Copernicus Climate Change Service, which monitors Europe's climate, reported in its June 2026 bulletin published on July 9 that western Europe had its warmest June ever recorded. The average temperature over European land was 19.14°C — the second-highest for June in the records that exist. Worldwide, June 2026 was the second-warmest June on record (Copernicus). A follow-up report on July 14 confirmed the finding.

Why does extreme heat lead to violent storms? Think of the atmosphere like a pot of water on a stove. The longer and more intensely the sun heats the ground, the more the air above it warms and becomes unstable — just like water starting to boil. When there is enough moisture in that warm air and something pushes it upward (like a weather front moving in), all that built-up energy bursts out as powerful thunderstorms. The large hail in France — 5 to 7 centimetres across — would have needed updrafts (upward air currents inside the storm) of about 30 metres per second to keep the hailstones suspended long enough to grow that big. That is extremely fast — roughly the speed of a strong gust of wind in a hurricane.

The damage seen across the region, from broken car windows in France to flooded tram lines in Poland, shows the double threat that comes after a long heatwave: violent storms with large hail on one hand, and flooding from sudden, heavy rain on the other. One thing worth noting: The Guardian's Weather Tracker column does not name any specific weather agency, database, or official source for its storm coverage. The French, Polish, and Copernicus information cited above comes directly from those agencies' own weather bulletins, forecasts, and climate reports — not from the Guardian article.

What does this mean for the weeks ahead? The heatwave has lasted into mid-July, and the moist air flowing in from the Atlantic that Poland's weather service flagged suggests the storm risk across central and western Europe probably will not go away soon. Weather services across the region are keeping their warning levels high. This combination of record heat followed by severe storms puts pressure on roads, power grids, farms, and public safety all at the same time. The vineyard damage in Ardèche is an early sign of how farming losses could build up as the growing season continues under these conditions.