The KNMI weather bureau, research institute TNO, health institute RIVM and the VU university have joined forces to develop a new system to warn people about the dangers of the increasingly hot weather.

Police officers who are out and about in uniform, runners and festival goers are just some of the groups that could profit from the new heat impact index, the researchers say.

“We often just look at the temperature,” TNO researcher at TNO Boris Kingma told  regional paper the Gelderlander. “But other factors, such as humidity and wind are just as important for the impact of heat on the human body,” he said.

The index measures the risk in numbers up to 13. “It may look a bit odd now that it’s December but we see that climate change is increasing the number of hot days,” Kingma said.

Very often heat warnings are aimed at the elderly but people who wear uniforms, and participants in sports and walking are also at risk. “Heavy protective clothing increases the risk of heat stress enormously,” Kingma said.

The heat impact index will enable the government and employers can help staff protect themselves from the heat. “By adapting work spaces staff will remain productive, even in high temperatures,” TNO work hygiene expert Jody Schinkel said. Unions are happy as well, he said, because the index will show a clear limit, beyond which workers will become ill from heat stress.

The KNMI wants to include the index in its green, amber and red warning system for dangerous weather. Next year the police, fire service, military police as well as the water boards and organisers of big festivals will cooperate in a trial run.

The RIVM said it hoped people would take the warnings seriously. “Many people think advice such as “drink enough water” or “keep your house cool” is condescending,” Werner Hagens of the Nationaal Hitteplan, which also warns about the dangers of high temperatures, said. “With this index, we can involve people more actively, for instance by asking them ‘Are you heat fit?’,” he said.

An extra index in addition to warnings about UV radiation intensity and codes yellow and red will not be confusing, Kingma said. “Every index has a different focus. UV intensity is about the risks of skin cancer while heat impact is about the physical impact of heat on the body. The warnings complement each other.”