The heat index is used to calculate not the actual temperature of the air around you, but instead how hot you feel. This all comes down to sweat.

The temperature on a summer day may be in the 80s or 90s. So why does it feel so much hotter? That's the heat index. Here's how it works.

Revise what latent heat is and how it relates to the changes in state, energy and mass of different materials as part of National 5 Physics.