People will soon be able to assess how oppressive summer weather is and adjust their activities using a new scale. Het Koninklijk Nederlands Meteorologisch Instituut (KNMI) will launch the hittekracht-index on Tuesday 2 June. The indicator will appear directly in the app of the weather institute.
The index runs from 0 to 10, following a similar structure to existing scales for windkracht and zonkracht. Rather than looking at temperature alone, the gauge calculates values using a combination of air temperature, humidity, wind, and solar radiation. KNMI and Universiteit Twente researcher Carolina Pereira Marghidan explained that identical temperatures can feel completely different depending on environmental factors. For example, a cloudy and windy 25°C day might rank as a 4, whereas a humid, still, and sunny day at the exact same temperature could spike to a 7.
Meteorological data meets human biology
The scientific foundation of the scale relies on the Wet-Bulb Globe Temperature, an international standard for measuring heat stress on the human body. The KNMI has translated this into an index of 0 to 10. Historical climate data shows that during heatwaves over the past thirty years, the index usually peaked at a 6 or 7. The maximum level of 10 remains exceptionally rare. It has never occurred in the north or west of the country, and it has registered for only four hours in De Bilt since 1991. Because these extreme peaks usually last for only a few hours, the KNMI will not link the index to its severe weather warning system of codes geel, oranje, and rood.
The index acts as a general guide because heat tolerance varies heavily between individuals. Boris Kingma, a thermal physiologist at Nederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek (TNO), noted that age and physical fitness dictate how a person handles heat strain. He compared the metric to how different skin types react to sun intensity. A spokesperson for the KNMI added that the public will need time to get used to the term, but they will eventually learn how each rating affects their personal well-being.
@ anp | NEWS BRAINPORT
