KNMI issues code yellow heat warning as temperatures reach 35 degrees
The Netherlands will face several more days of heat as the National Institute for Public Health and the Environment (RIVM) activates the National Heat Plan starting Tuesday, and the KNMI issues a nationwide Code Yellow weather alert.
The heat will be most intense in the south, east, and urban areas, while the Wadden Islands will remain relatively cooler, according to the Royal Netherlands Meteorological Institute (KNMI).
There has also been heavier traffic reported toward the Noord-Holland beaches and dunes west of Alkmaar compared to an average Tuesday afternoon.
Ttemperatures in the south will reportedly peak at 33 to 34 degrees on Tuesday. On Wednesday, most inland areas will exceed 30 degrees, with parts of the east reaching 35 degrees.
Warm nights are expected, with minimum temperatures between 15 and 20 degrees, and urban areas cooling no further than about 20 degrees.
The night into Thursday is expected to be the warmest of the week. Rising humidity will reportedly make conditions feel even more oppressive, and thunderstorms may develop on Thursday.
RIVM warns that extreme heat can be dangerous, especially for elderly people and those with vulnerable health conditions. Even healthy individuals risk dehydration and overheating during heavy physical activity.
Officials urge the public to avoid direct sun, stay hydrated, limit strenuous activities during the hottest hours of the day, and ensure homes remain cool. Special attention is advised for neighbors who may need assistance, and for pets. Authorities emphasize that children and animals should never be left in closed vehicles, even briefly.
Cities are expected to experience higher temperatures than surrounding rural areas due to the so-called urban heat island effect. This phenomenon occurs because buildings and infrastructure both generate and retain heat, often creating a temperature difference of several degrees compared to the countryside.
The decision to activate the National Heat Plan was made after consultations between the RIVM and KNMI, reportedly taking into account not only the forecast high temperatures but also expected night temperatures and humidity levels. The plan aims to reduce health risks by increasing public awareness and encouraging protective measures.
A new heat stress index, currently being developed by KNMI in collaboration with TNO, RIVM, and Vrije Universiteit, is expected to launch in summer 2026. Known as “hittekracht” in Dutch, the index will combine temperature, humidity, solar radiation, and wind to better assess how burdensome heat feels to people.
KNMI notes that the National Heat Plan is not the same as a heatwave. A heatwave in the Netherlands can only be confirmed after it has occurred and requires at least five consecutive days in De Bilt above 25 degrees, including at least three days above 30 degrees.
