The most severe part of the front has hit areas between Ballarat and Geelong including Dereel, Linton and Rokewood.

The front is now pushing towards Bacchus Marsh, the Brisbane Ranges and areas including Geelong's northern suburbs by 4.20pm.

Power outages have also been reported in Ballarat's west and areas west of Ballarat, although it is known if the storm was the cause.

EARLIER:

A severe thunderstorm warning has been formally issued by the Bureau of Meteorology as a line of storms crosses the state.

Severe thunderstorms are likely to produce damaging winds, large hailstones and heavy rainfall that may lead to flash flooding over the next several hours.

Locations which may be affected include Ballarat, Bendigo, Maryborough, Castlemaine and Bacchus Marsh.

The State Emergency Service advises that people should:

Meantime, an advice alert for potential Thunderstorm Asthma been issued for central parts of Victoria, including the Ballarat region.

Chief Health Officer, Professor Brett Sutton also issued a high risk alert on Thursday afternoon, meaning there is an increased chance of an epidemic thunderstorm asthma event occurring.

It comes as the city prepares for the possibility of severe thunderstorms which could bring damaging winds, large hailstones and heavy rainfall.

What is thunderstorm asthma?

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.

Who is at risk?

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

Thats why its 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.

EARLIER:

Severe thunderstorms are likely to hit Ballarat today, according to the Bureau of Meteorology.

While thunderstorms are predicted over much of Victoria, Ballarat and surrounding areas have been highlighted as the main area of concern.

A severe weather warning has not yet been officially issued, although they could be released as the day progresses.

Damaging winds, large hailstones and heavy rainfall are likely to fall in the 'red' area on the map above, of which Ballarat appears in the middle.

The forecast follows spectacular storms that hit the region last night, resulting in sporadic bursts.

There were some reports of large hailstones in many regions surrounding Ballarat, although the city itself seemed to mainly escape major damage.

The temperature is forecast to hit 28 degrees in Ballarat today, with the storms to hit in the afternoon and evening.

Friday and Saturday are expected to be considerably cooler and more stable, with forecast maximums of 21 and 17 degrees over the next two days.

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