What three factors determine the probability of ignition in wildland fires?

The probability of ignition in wildland fires is primarily influenced by the characteristics of the fuel and environmental conditions that affect those fuels. Fuel shading refers to how the presence or absence of larger vegetation can influence moisture levels in the smaller, more readily ignitable dead fuels. Fine dead fuel moisture percent is crucial because it indicates how moisture content can affect the ease with which these fuels will ignite. Dry bulb temperature is the measure of air temperature without the influence of humidity, and higher temperatures can facilitate the drying of fuels, making them more susceptible to ignition.

Combined, these factors create an environment that can either promote or inhibit ignition. Higher temperatures and lower moisture levels in fine fuels, influenced by shading from larger vegetation, significantly increase the likelihood of ignition occurring in wildland fire scenarios.