Trees have a natural moisture content level that fluctuates year round, and the actual moisture content of the wood can vary depending on the species of tree and how healthy it is.
The starting moisture content of wood can also be influenced by the time of year the wood is cut. Natural moisture levels of trees are higher during the spring and summer months but drop during winter.
It’s therefore preferable to cut wood during winter when moisture levels are at their lowest. The seasoning process can then be started in early spring, and the upcoming warmer weather and lower starting moisture content helps to speed up how quickly the wood dries out.
Whatever time of the year wood is cut, it will have a moisture content that is far too high for it to burn efficiently on a fire.
In order for lumber to reach this moisture content range, it must be dried through a process known as seasoning, where the lumber is left outdoors in the right conditions to naturally lower the lumber's moisture content over a period of time.
The time it takes for wood to dry to the recommended moisture content can vary depending on a number of factors. After the same amount of time, some logs may still be too wet to use as firewood and some may have reached the recommended moisture content.
The moisture content of properly seasoned firewood will also be around 15-20%, which is the recommended moisture content for firewood, but the time it takes for wood to reach this level can vary.
The moisture content of seasoned wood will never fall below a certain level. The humidity of the atmosphere means that seasoned firewood will always retain some moisture. In our experience, we've found that some of our seasoned firewood has never dropped below 10%, even though it was fully seasoned several years ago.