Worldwide, attention is being drawn to the risks of extreme heat today, on Heat Action Day. This is necessary: due to climate change, we are increasingly facing extreme heat in the Netherlands. But when does it really feel hot? Together with TNO, RIVM, and VU, we are developing heat power to better assess how burdensome heat is for humans.
Not All Heat Feels the Same
A dry summer day at 30 degrees with a breeze feels very different from a muggy day at 25 degrees without wind. However, heat is often assessed based on temperature alone. This does not provide a complete picture. How hot it feels to your body also depends on humidity, solar radiation, and wind.
You can see this difference, for example, at sports events. Recently, heat has caused problems there more often, such as a few weeks ago in Leeuwarden and Leiden, when athletes became unwell due to the heat at various running events. But not only athletes are at risk: emergency services such as police, fire department, and ambulance personnel sometimes work outside for long periods in heavy clothing and can suffer from the heat. For all these groups, a more accurate measure than temperature is needed to properly assess risks and take timely action.
Temperature, Humidity, Solar Radiation, and Wind
Fortunately, there are international standards to better determine the burden of heat on the human body. The Wet-Bulb Globe Temperature (WBGT) is such a scientifically grounded measure, which combines temperature, humidity, solar radiation, and wind. This has been used internationally for decades to estimate the impact of heat for, for example, defense, labor, and sports.
The KNMI now calculates the WBGT specifically for the Netherlands, data that is publicly available via our Data Platform. However, the measure is somewhat difficult to interpret because it results in a lower value than the actual temperature due to the calculation. This feels contradictory. Therefore, we are working on an accessible version for the general public: heat power. This converts the complex WBGT value into an understandable scale of 1 to 10, similar to sun strength and wind strength, so that everyone can see at a glance how burdensome the conditions are. KNMI is currently working on converting the WBGT to a practical 1-10 scale.