Wildland firefighter safety is influenced by sudden, unexpected changes in wildfire behaviour. Typically, these changes are brought about by sudden increases in wind speed and changes in wind direction. These changes can generally be predicted or anticipated. Cold fronts passing through can be predicted, sudden increases in wind speed or directional changes can also be anticipated from convective activity (e.g., thunderstorms). Cold fronts and convective activity tend to be visible to firefighters and because of this they are able to take precautions. Far less common, and generally not visible, are changes in wildfire behaviour caused by the extreme instability of the lower atmosphere. This instability can be caused by what is referred to as super adiabatic lapse rates, which are generally due to the extreme heating of the earth’s surface in calm conditions.