Epidemic thunderstorm asthma

On Nov 21, 2016, Melbourne (VIC, Australia) was experiencing the peak of an unprecedented spring heatwave. Temperatures that day climbed to 35°C, the hottest recording since March that year, and the pollen count was extremely high, with airborne ryegrass pollen concentrations of more than 100 grains per m3 of air. Around 1400 h, the Australian Bureau of Meteorology issued warnings across most of the state for severe thunderstorms with damaging winds. Between 1700 h and 1830 h, the temperature suddenly dropped from 35°C to the low 20s and thunderstorms started to erupt, sending severe gust front winds over Melbourne's metropolitan area.