You will find much better, more scientific definitions in physics sites, but the following are supposed to be straightforward and clear. Relative humidityīefore going a bit more into dew point, it's important we understand two concepts clearly. If you look closely, you will notice that the dew point line is basically the same as the temperature but a few degrees below it. There is no artificial humidifying or dehumidifying or heating or cooling. This is a space without any HVAC control. In other words, it is not something you want to be too close to your dry air temperature if you want to keep your things dry.If your dew point is well below the dry air temperature, your RH is low.If your dew point temperature is close to your dry air temperature, your RH is high.This means that the dew point is the temperature at which dew will begin forming in your space.Dew point is the temperature at which Relative Humidity (RH) in your space is at 100% so that the moisture will start condensing out of the air.It represents the absolute moisture content of the air.What does it tell us? I have found several explanations of dew point, so I will attempt to sum it up here as clearly as possible: The dew point line, and this line can be a bit trickier to interpret. What is the dew point, in simple terms? When you look at your environmental monitoring charts, you are used to seeing the temperature and relative humidity lines. What can the psychrometric chart do for you?.A psychrometric chart and dew point example.The psychrometric chart again in full colour.