"It's not the heat, it's the humidity!" We've all said it, but is it true? Just what does it mean?

In this feature we are going to try and explain some of the weather terms we hear so often, and a few we hope to never hear. If you have weather words or phenomenon you'd like to know more about - let us know. We'll check with our experts and get the answers for you.

Humidity - This is a measure of the water vapor content in the air. They will usually list it as a percentage - 60% humidity for example means that 6 out of 10 particles of air include moisture. Although it changes with each individual person, in general, people begin to feel uncomfortable when the Humidity is at or above 70%.

Dew Point - Similar to humidity, this is the saturation temperature, it measures airborne moisture. The higher the dew point, the greater the moisture content of the air

Heat Index - Similar to winter's "Wind Chill Factor" the heat index is the temperature we feel after factoring in both actual temperature and humidity.

Heat Lightning - This term usually applies to lighting that is not accompanied by thunder - or at least not that we can hear. In reality, the thunderstorm is out of our hearing range but because of the extra hot conditions the lightning can be observed from quite a distance.