What most directly affects the growth of a wildland fire?

The growth of a wildland fire is most directly influenced by weather conditions and topography. Weather conditions, including temperature, humidity, wind speed, and precipitation, play a crucial role in determining how easily a fire can ignite and spread. For example, high temperatures and low humidity can dry out vegetation, making it more susceptible to ignition, while strong winds can carry embers over long distances, leading to rapid fire spread.

Topography also significantly impacts fire behavior. The slope of the land can steer the fire's direction and intensity; fires often move faster uphill due to the preheating of fuels above the flames. Conversely, lower areas or valleys might act as barriers to fire spread.

By considering both weather and topography, firefighters can better predict fire growth and behavior, allowing for more effective fire suppression and management strategies.