Belgium Misses a Second Official Heatwave as Ukkel Peaks at 29.1 Degrees
The temperature at the KMI reference station in Ukkel peaked at 29.1°C on Wednesday 16 July 2026, falling 0.9 degrees short of the 30-degree threshold needed to declare a second official heatwave of the summer, Belgian media reported citing KMI measurements.
Heatwave declarations in Belgium are not just labels: they anchor the national climate record and shape how warm summers are compared across decades. The 0.9-degree miss illustrates both the precision of the Ukkel benchmark and the reality that heat stress on residents, workers and vulnerable groups does not wait for an official threshold to be crossed.
Ukkel (Uccle in French) is a Brussels municipality that hosts the headquarters and reference weather station of the KMI/IRM, Belgium's Royal Meteorological Institute. Its measurements serve as the country's official climate benchmark: national records, seasonal statistics and heatwave declarations are all based on readings taken there. Under the KMI definition, a Belgian heatwave requires at least five consecutive days of 25°C or more at Ukkel, including at least three days of 30°C or more. On 16 July 2026 the station peaked at 29.1°C, so the second heatwave of the summer was not declared, according to De Standaard, Het Nieuwsblad and De Morgen, all citing KMI data.
Background
Belgium has used Ukkel as its reference station for more than a century, allowing consistent comparison of warm episodes such as the benchmark summers of 1976, 2003 and the record-breaking heat of recent years, when Ukkel first passed 40°C in July 2019. KMI climate reporting documents a clear trend toward more frequent and more intense warm spells at the station over recent decades, which is why near-misses of the heatwave threshold now draw close public attention.
What to do
Heat advice applies regardless of the official label: hydrate, check on vulnerable neighbours and relatives, and follow guidance issued under Belgium's heat and ozone plans, which are activated by forecast conditions rather than the heatwave designation.
Impact
Regional — The measurement itself is taken in Brussels, but its significance is national: Flanders, Wallonia and the capital all read their summers through the Ukkel station. Local temperatures elsewhere in the country may have exceeded 29.1°C, but only the reference station counts for the official record.
Opposing perspectives
- KMI meteorologists on threshold rigour
Meteorologists at the KMI defend the strict Ukkel-based definition: because the same station and the same thresholds have been used across decades, a declared heatwave in 2026 is directly comparable with those of 1976 or 2003. Loosening the criteria whenever a warm spell narrowly misses would erode the value of the national climate record, in their view — a 29.1-degree day is hot, but the threshold exists precisely so the statistics remain meaningful.
- Climate researchers and public-health voices
Belgian climate scientists and public-health institutions such as Sciensano, which monitors heat-related health effects, emphasise that the binary heatwave label understates real-world risk: mortality and health impacts among the elderly and chronically ill rise well below the 30-degree mark, which is why Belgium's heat and ozone plans are triggered by forecast conditions rather than the official heatwave designation. For them, the near-miss is a statistical footnote to a genuinely stressful warm spell.
Sources & evidence
- View sourceDe Standaard — Geen sprake van tweede hittegolf in België: 29,1 graden in UkkelPrimary· standaard.be· 16 July 2026Retrieved 16 July 2026· 1 day ago· Dated
- View sourceHet Nieuwsblad — Net geen officiële hittegolf: 29,1 graden gemeten in Ukkel· nieuwsblad.be· 16 July 2026Retrieved 16 July 2026· 1 day ago· Dated
- View sourceDe Morgen — Live: Geen hittegolf, temperatuur in Ukkel blijft steken op 29,1 graden· demorgen.be· 16 July 2026Retrieved 16 July 2026· 1 day ago· Dated
- View sourceKMI/IRM — Koninklijk Meteorologisch Instituut van België (heatwave definition and Ukkel climate data)· meteo.beRetrieved 16 July 2026
