As wet and wild weather lashes much of eastern Australia, health authorities are warning people to be on alert this thunderstorm asthma season.

Thunderstorm asthma season has arrived and the risk of deadly events is tipped to be higher than normal with a wet end to the year forecast.

The Bureau of Meteorology is predicting heavy spring rainfall for much of the country, increasing the risk of thunderstorm asthma events in late spring to early summer.

"Forecast wet and warm conditions will lead to good grass and vegetation growth over the spring period and this forecast is largely driven by a negative Indian Ocean Dipole, which is the first negative IOD event since 2016," senior forecaster Keris Arndt said.

Ten people died during or soon after the thunderstorm asthma event in Melbourne on November 21, 2016, with about 1400 people also treated in hospital.

Those affected included people with and without a history of asthma, those with undiagnosed asthma and others with seasonal hay fever.

National Asthma Council Australia director Professor Peter Wark said those with hay fever and allergies to ryegrass pollen may be at risk of thunderstorm asthma, even if they have never experienced asthma symptoms before.

The respiratory physician reminded asthma suffers living in or travelling to a region with seasonal high grass pollen levels to take their inhaler.

"These steps offer the best protection from worsening asthma," he said.

Prof Wark also advised asthma or hay fever sufferers to check online grass pollen counts for their region each day and stay inside as thunderstorms approach, particularly during wind gusts just before rain fronts hit.

As wet and wild weather lashes parts of eastern Australia, epidemic thunderstorm asthma season officially begins on Friday and runs until the end of December.