This seminar is part of the USFS Missoula Fire Lab Seminar Series.

Wildland fire potential is best described as a combination of available fuels, suitable weather conditions and sources of ignitions and weather is the most spatially and temporally variable of these three components. Weather variables such as temperature, relative humidity, precipitation and wind speed independently influence wildland fire spread rates and intensities, and the alignment of multiple weather extremes, such as the co-occurrence of hot, dry and windy conditions leads to the most severe fires. Many systems have been developed to integrate these critical weather variations into predictions of wildland fire potential. These ‘fire danger rating systems’ are used worldwide to prepare for and respond to wildland fires. Here we briefly introduce some common fire danger rating systems in use throughout the world and we show how these systems can be used to examine historical changes in wildland fire potential. We detail the development of generalized metrics of fire weather season length and we explore their global spatial and temporal variations. We show how these metrics can account for much of burned area variations recorded across North America and Europe and we show that fire weather seasons are lengthening globally and have increased by nearly 20% from 1979-2013. Most of these fire danger rating systems have remained static for decades despite scientific advances that could lead to major improvements in fire potential assessment. Therefore, we close by introducing the next-generation of the US National Fire Danger Rating System, NFDRS2016, and we detail how these improvements will lead to a more robust and user -friendly system that can improve our ability to plan for and respond to wildland fires and ensure the safety of wildland fire personnel nationwide.