A ‘moderate’ warning for thunderstorm asthma has be issued for much of Victoria today.

The Department of Health and Human Services in conjunction with the Bureau of Meteorology has declared Central, North Central and Northern Country Victoria “a moderate risk for Epidemic Thunderstorm Asthma”.

This includes Ballarat and all other areas within the orange zone below.

The forecast predicts the risk of an epidemic thunderstorm asthma event for the current day, the next day and the day after that, using a colour coded scale of green (low), orange (moderate) and red (high).

Rain is forecast to hit Ballarat later this evening, although thunderstorms are not expected, according to the Bureau of Meteorology.

A lack of an early warning system was a key factor in the freak thunderstorm asthma outbreak last November that killed nine people in Melbourne and landed about 8500 in hospital.

The Ballarat Base Hospital also recorded one of it’s busiest nights in history.

The “moderate” warning means asthma sufferers should be prepared and know what to do if the weather does cause concern.

Asthmatics and people who experience bad hay fever are urged to take precautionary measures now.

During grass pollen season people may notice an increase in asthma and hay fever. Grass pollen season also brings the chance of thunderstorm asthma.

Thunderstorm asthma is thought to be triggered by a unique combination of high grass pollen counts and a certain type of thunderstorm.

For people who have asthma or hay fever this can cause severe asthma symptoms, making it difficult to breath.

When a large number of people develop asthma symptoms over a short period of time, this is known as epidemic thunderstorm asthma.

These epidemic thunderstorm asthma events don't happen every year but when they do, they can happen during grass pollen season, which is normally from October through December. 

Thunderstorm asthma can affect those with asthma or hay fever - especially people who experience wheezing or coughing with their hay fever.  

That’s why it’s important for people with asthma or hay fever to know about thunderstorm asthma and what they can do to help protect themselves during grass pollen season.

Even if you don't think you have asthma or hay fever, don't ignore symptoms like wheezing or shortness of breath - check with your GP.  

To access the forecasts, Victorians can download the Vic Emergency App or visit: www.emergency.vic.gov.au/prepare