The 2016 epidemic thunderstorm asthma event in Melbourne, Australia, highlighted human vulnerability to poorly understood hazards (1). As described by Kornei, deploying early warning systems by combining meteorological forecasting and pollen monitoring is an important response to protect populations from future events (2). Yet effectively predicting thunderstorm asthma demands a deeper understanding of this phenomenon, particularly the cause of pollen rupturing; a process thought to be key because it transforms the cellular contents into aerosol fragments small enough to penetrate the lungs (3). A widely held view is that rupturing is associated with atmospheric moisture, either alone or in combination with the rapid changes in temperature and pressure associated with thunderstorm uplift (4,5). Yet we suspect the cause is more complex and puzzling than this simple association. While there is clear evidence that moisture can promote pollen rupturing under some circumstances (3,6), pollen grains are some of the most resistant biological products on earth and survive intact in waterlogged sediments for hundreds of thousands of years . Rapid changes in pressure and temperature also appear inadequate explanations because grains of multiple species have been shown to withstand analogous sharp shifts in pressure and temperature, both alone and in combination (7, 8). A key mechanistic factor thus appears to elude us: a factor that determines which pollen grains are liable to rupturing when. We suspect that in addition to pollen taxon (9), the developmental stage of pollen grain is of paramount importance. This is a highly plausible driver of variation in pollen grain susceptibility, particularly given apparent links between pollen rupturing and abortive germination (6). Its potential role in thunderstorm asthma, however, remains almost entirely unexplored. Resolving its importance could prove a critical precursor to reliably predicting thunderstorm asthma epidemic events.