There are a number of factors that cause wildfires to spread: weather (wind, temperature, and humidity), topography, times and seasons, fuels, and space between fuels. Wind provides fresh oxygen to a fire and wind can also cause a change in the direction of the fire or carry embers to new areas with more fuel.
Fire will burn more quickly up a slope because of the tendency for steeper slopes to have fuel in close proximity. The proximity of the fuel can cause a fire to speed up or slow down. Areas with lots of sun and higher temperatures tend to absorb moisture from fuels and make them easier to catch fire while areas located with high humidity and rainfall make fuels less likely to catch fire.
