The Waroona bushfire in Western Australia burnt 69,000 ha in January 2016, destroying more than 160 homes and causing two fatalities. During the first two days of the fire, there were four periods of extreme fire behaviour: two involving massive pyrocumulonimbus (bushfire thunderstorm clouds) and two major ember showers. This extreme fire behaviour was unexpected, so why did it occur? This Hazard Note details a case study that examines the meteorology and fire reconstruction in parallel, identifying the dynamic processes behind the extreme fire behaviour to provide valuable knowledge to apply during future bushfires.