Outlook for the 2019 grass pollen season

Sept. 23, 2019

Melbourne’s grass pollen season is fast approaching and while we’re not expecting much grass pollen in the air until later in October, the outlook is already for a heavier season than 2018.

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Maps showing soil moisture levels (left) and satellite images of vegetation greenness (right). Images provided by the Bureau of Meteorology and NASA/USGS.

Melbourne’s grass pollen season is fast approaching and while we’re not expecting much grass pollen in the air until later in October, the outlook is already for a heavier season than 2018.

So, what’s driving this outlook?

Melbourne has so far received less than half its annual average rainfall of 650 mm. This puts 2019 on par with 1967, Melbourne’s driest year (www.baywx.com.au) and low rainfall generally means less grass growth and less grass pollen.

But after one of the driest start to a year on record, autumn and winter rainfall have been close to average for much of Victoria.

As soils warm through early spring, the amount of water available to plants – the soil moisture level – is a major factor determining growth.

The first map shows moisture levels in soils across Victoria.

Pasture grasses in western Victoria are the source of much of Melbourne’s grass pollen. The large blue areas in the map show that there are above average levels of soil moisture in these grazing lands.

If that soil wetness translates into more grass growth, then that should mean more grass pollen as well this year.

Early indications are that western Victoria is already a lot greener than at the same time last year. This increased greenness is seen by comparing the satellite images from mid-August 2019 and 2018, which are taken at wavelengths that measure the greenness of plants.

This comparison is shown in the second set of maps.

Simply put, although 2019 has been a very dry year, the pasture grasses across western Victoria, the source of much of Melbourne’s grass pollen, are in good condition coming into spring.

And that growth is setting us up for a bigger grass pollen season than last year. That will mean more days with high or extreme levels of grass pollen, which are bad days for most people with hay fever or asthma.

Bad enough, but not a record season.

But this outlook isn't locked in. For instance, if spring rainfall disappoints there will likely be some reduction to the size of the 2019 season.

So, people with hay fever should learn asthma first aid, see their GP if they think they may also have asthma, follow their hay fever treatment plans and have asthma reliever medication suitably available.

And people with asthma should ensure they have had recent review with their doctor and achieved good control of symptoms. Also remember to take any prescribed preventer every day, even if no symptoms, have an asthma action plan that includes thunderstorm asthma, and always carry their asthma reliever with them.

Remember, everyone should avoid thunderstorms in grass pollen season (October to December) especially the wind gusts that proceed them.

We’ll start counting again across all eight Victorian pollen monitoring sites on October 1. Each day through to December 31 we’ll provide a daily grass pollen count and 7-day forecast for grass pollen.

Grass pollen counts and forecasts will be available on www.melbournepollen.com.au and via our free mobile app and are updated daily at around 10:30am.

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