Although human bodies have the same physiologic mechanisms across the globe, today you can find numerous thermal indices that measure the complex conditions of heat exchange between the human body and its thermal environment. As heatwaves are becoming a permanent threat during the summer, it is important for citizens to understand what “felt temperature” exactly means, how it is measured and why such indices can help employers and government authorities to understand our bodies’ limits when it comes to heat load and uses the index to set boundaries.