Obviously, the amount of water that is in the air affects its drying ability. Less water results in a lower vapour pressure and a better chance that the grain vapour will overcome it. But how does one determine the amount of water in the air. It turns out that it isn’t that onerous. When air is holding the absolute most it can hold, it is said to be in saturation. The saturated amount of water that air can hold is determined almost exclusively by its temperature and it can be obtained from something called a psychrometric chart. The formula for this is:
Ws = 0.000289 *T3 + 0.010873 * T2 + 0.311043 * T + 4.617135
Where Ws is the saturated amount of water (grams) per cubic meter at a given temperature, T (degrees Celsius, ⁰C).
If air is cold, it cannot hold much water. At 0 ⁰C the most it can hold is 4.6 gr/m3 whereas when the air is hot at 35 ⁰C it can hold almost ten times that at 41.2 gr/m3.