Occasionally the weather can play a major role in asthmatic reactions and event respiratory deaths.

Melbourne, Australia recently (11/2016) reported many flares in asthma, and numerous deaths after a freak thunderstorm. It is hypothesized that thunder can affect the size of pollen — making them small enough to be very problematic, sometimes even in people previously undiagnosed with asthma. The pollen which was high in Melbourne at the time was rye grass.

Olive tree pollen was implicated in a previous episode in Italy, and Hormodendrum (Cladiosporium) is a mold which has been inplicated in hospitalizations in the US.