Common advice during summer heat is to close windows and shutters during the day. But Kachelmann says this is not always the right approach, particularly for older people who spend the whole day at home in small homes.
His argument is that air needs to circulate when people are at home. Humidity also plays a role alongside heat and can become a problem in small rooms without ventilation if the windows remain closed for hours.
"The killer is not the temperature, it is the humidity," he argues. Closing windows all day makes sense when nobody is at home, but the situation should be handled differently when people are inside.
Kachelmann also wants to clear up a common misconception about forest fires. High temperatures alone are not enough to cause a wildfire, he says.
According to the meteorologist, two factors are needed for a fire: it must be dry and there needs to be an ignition source of around 250 to 300 degrees. A natural source of ignition could be lightning during a thunderstorm. Otherwise, humans are responsible, consciously or otherwise, he says.
He wants to push back against the term "Hëtztbrand", or heat fire, as heat alone is not the source. He also rejects the idea that a shard of glass could cause a fire in a forest.
Kachelmann also warns against confusing heat with drought.
When rivers and other natural water areas start to dry up, this is not a consequence of a heatwave but of a lack of rain. This will become evident next week when temperatures drop but water levels do not rise.
Rain is desperately needed, says Kachelmann.
But the outlook is not promising, he explains. There could be local showers which would improve the situation a little, but they will not be enough to end the drought.
"Heavy rain is still not in sight," he tells RTL.
