Note on the graph you can read by Fahrenheit or by Celsius. The graph helps us understand how relative humidity can cause health impacts at lower temperatures. Be sure to read through the first document above about symptoms of heat stroke in children, seniors, and adults.
Note to Europeans: I have been watching news about what is happening there. I see so many standing or hanging out in the sun. Also, many people are wearing dark colors. Keep physical exertion minimal; swimming laps is not very effective because you are stressing your body. Get out of the sun into shade, wear white or light colored, light weight clothing, and hydrate over the day. Look for rehydration tablets with electrolytes. Understand how easy it is to get into trouble. Our bodies have limits on internal temperature. Read the guidelines above. Children are particularly vulnerable to heat as are seniors and people with respiratory disorders.
Look on Amazon by country for rehydration tablets or beverages with electrolytes.
Here is the Amazon link on U.S.
Here is the Amazon link in UK.
Here is the Amazon link for India.
Susan Feathers 
Good to bring attention to this reality. And thinking of our European friends not set up to manage this kind of heat. Relative humidity is very much a factor so glad you drew attention to that. Betty
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