This FACT indicates the average annual afternoon relative humidity measured at 3pm in each Australian city between the years 1893 and 2010. Note that each city has various lengths of records kept. The relative humidity measures the amount of water vapour in the air as a percentage of the maximum water vapour the air can hold. Therefore relative humidity is measured as a percentage. A relative humidity reading of 100% means that the air is completely saturated with water and cannot hold anymore. Relative humidity near the ground could be much less, therefore there does not need to be a reading of 100% for it to be raining. The city with the highest humidity is Hobart at 58 percent, followed closely by Sydney at 57 percent. The cities with the lowest are Adelaide and Canberra at 47 percent.