Ozone concentration levels in Belgium exceeded the European threshold limits in two locations on Friday at 5.00 p.m., the Inter-regional Environment Cell, Celine, reported on Twitter.
The threshold is 180 microgrammes per cubic metre (180 µg/m³). When it is exceeded, high-risk populations such as children, the elderly and people with breathing problems are advised to avoid excessive physical activity outdoors.
On Friday afternoon, measurements of 183 µg/m³ and 189 µg/m³ were registered in Bree (Flanders) and Dressel (Limburg) respectively.
The threshold could still be exceeded in the next few hours, Celine warned.
The service had already warned on Thursday that high concentrations of ozone were expected on Friday given the very hot, sunny weather forecast.
The local record for maximum temperatures was broken in Uccle at about 1 p.m., where a high of 32.4°C was recorded. The previous record of 31.7 °C dated back to 1943.
A little before 6.00 p.m., the highest maximum temperature recorded at the Royal Meteorological Institute’s measuring stations was 36.9°C in Beitem, Western Flanders, meteorologist David Dehenauw announced on Twitter.