Dry wood catches fire between about 300 degrees Fahrenheit and 580 degrees Fahrenheit, depending upon the species of wood and the extent of decay present, with more decayed wood being quicker to ignite. The amount of moisture in the wood is the strongest influence on wood reaching this temperature.
When heat is applied to a piece of wood, it gradually rises in temperature. Around 212 degrees Fahrenheit, the water present in the wood starts to boil and evaporate. Most of the heat energy applied to the wood goes towards heating the water until it is completely dry.
If the heat source runs out of energy before the water is evaporated, the wood never catches fire. Therefore, wood must be dried prior to ignition. This is one of the primary reasons that people split firewood as they do. By opening the middle of the log, the wood fibers, or xylem, are in greater contact with the air. This increase in airflow causes the wood to dry out more quickly than if it were still intact. Additionally, people often stack their firewood to ensure that air flows all the way around it and the wood does not absorb water from the ground.