"Thunderstorm asthma" triggered more than 1,900 calls to Ambulance Victoria on Monday night. But what exactly is thunderstorm asthma? And what should you do if you have it?

An unprecedented spike in a rare phenomenon called "thunderstorm asthma" was reported in Melbourne, Australia on November 21, 2016 after wild storms swept through the region, abruptly ending one of the city's hottest days of the year. By the day's end, two people have died, but the number might still rise.

Rain and strong winds on Monday afternoon churned up pollen and other irritants causing a flood of calls to Ambulance Victoria from asthma sufferers.

Assoc. Prof. Ed Newbigin speaks about thunderstorm asthma

Are you a hayfever sufferer? Would the app be helpful to you?

Attention all hayfever sufferers.

If you've noticed yourself sneezing and sniffling this year more so than last, you're not imagining things.

Hayfever symptoms are expected to get worse during November.

Rain during the winter and spring months has encouraged plants and grass to grow resulting in increased pollen across the region.

If you feel like you’ve spent all spring mid-sneeze, you’re not the only one. Friday saw Melbourne’s highest pollen count since November 2013.

Monday's pollen count was “extreme” according to Melbourne Pollen Count and Forecast, a free website and app by Melbourne University’s School of Botany and Asthma Foundation Victoria, which recorded 154 grass pollen grains per cubic metre.

Warnings that 2016's hayfever season would be the worst in years have come to pass, with sufferers across Melbourne reporting severe symptoms.

Melbourne University botanist Associate Professor Ed Newbigin warned earlier this year that the city's hayfever sufferers were set for a worse-than-usual season.

If it seems like there are more people sniffling in your office, itching their red eyes in your uni tutorials or snorting nasal spray on your train ride home, it’s because today we’re experiencing something of a hay fever apocalypse.