Heatwave Gives Way to Violent Storms Across Belgium

After days of record-shattering heat that pushed temperatures to nearly 40°C, violent thunderstorms swept across Belgium on Saturday, bringing hailstones the size of marbles, heavy rainfall, and a sharp surge in emergency calls. The Royal Meteorological Institute (IRM/KMI) issued yellow warnings for Walloon provinces as the country transitioned abruptly from extreme heat to severe storms.

Record-Breaking Heat

June 26 was the hottest June 26 since records began in Belgium, with the Kleine Brogel weather station recording 39.97°C — just shy of 40°C. The heat dome that parked over Western Europe broke numerous national records, including Germany’s all-time high of 41.3°C, Switzerland’s 38.8°C, and the Netherlands’ June record of 38.2°C. The UK recorded three consecutive June temperature records.

According to a rapid attribution study by World Weather Attribution, the same weather pattern now produces temperatures about 3.5°C hotter during the day than in 1976. The study found that the 2026 June temperatures would have been “virtually impossible” to occur in 1976, and that daily maximum temperatures are warming at about triple the rate of global warming.

Storm Transition

As the heatwave broke, two storm episodes were forecast for the weekend. The first, hitting Saturday evening through early Sunday, brought intense downpours and hail. The VRT NWS liveblog reported storms breaking out above Ostend, with hailstones as large as marbles in the Westhoek region. Sunday afternoon storms were expected to be more intense in Liège, Luxembourg, and Namur, with up to 70 litres per square metre of rain and strong wind gusts.

The non-emergency number 1722 was activated for storm and flood damage assistance to prevent overloading 112 emergency lines, RTBF reported. The Service Public de Wallonie noted that river levels were low and soils dry enough to absorb the rainfall, meaning no river flooding was expected.

Healthcare System Under Strain

Emergency calls to 112 surged by over 40% during the heatwave peak — from an average of 1,000-1,100 per day in mid-June to 1,836 on Thursday June 25 alone. Fire brigade interventions in Brussels more than doubled, rising from 40 on June 3 to 87 on June 24.

According to RTBF, geriatric wards were at 90% occupancy on average, and four additional ambulances were deployed in Brussels, including one staffed by Red Cross volunteers. Philippe Devos, Secretary General of the private healthcare federation, warned of a cumulative effect: “There is a cumulative effect of sleep deprivation linked to extreme nighttime heat. And it’s often after five or six days of heatwave that serious problems begin.”

Human and Wildlife Toll

A 50-year-old Polish seasonal worker died on a courgette field in Zonnebeke, possibly due to the heat. In neighbouring France, at least 40 heat-related fatalities were reported, and a baby died after being left in a car in Marseille.

In Kapelle-op-den-Bos, a 1-metre sturgeon died from heat stress in a pond owned by alderman Dirk Hermans. The fish had lived there for nine years. “I will stop keeping a sturgeon; they are too sensitive to the heat and this won’t be the last heatwave we experience,” Hermans told VRT NWS.

Climate Inequality

The heatwave has also laid bare deep social inequalities. An RTBF investigation cross-referencing satellite land temperatures, income data, and vegetation coverage found that wealthier Belgians are far better protected against extreme heat in urban areas, with better access to green spaces, cooling, and resilient housing.

What’s Next

Belgium’s National Heat and Ozone Plan remains in its alert phase, activated on June 23. With the second storm episode expected Sunday and further heatwaves likely this summer, the strain on healthcare services, infrastructure, and vulnerable populations is expected to continue. As VRT NWS meteorologist Bram Verbruggen noted: “You can really see climate disruption at work. In the future, we will get more weather blockages, causing warm air to linger longer and heat up further.”

The World Weather Attribution study concluded starkly: “This summer shows that at 1.4°C of global warming, extreme heat is already reaching the limits of our societies’ ability to cope.”