It has been 15 years since Ballarat has experienced as much rain as it has had so far this year, and don't expect it to stop any time soon.

To date, 464mm of rain has been recorded in Ballarat this year _ the highest the running total has been since 1996.

This is about double last year's total to August 14, when only 237mm had been recorded.

Meteorologist Harvey Stern, from the Bureau of Meteorology, said a La Nina effect was sweeping the east coast of Australia.

''The weather has shifted to a La Nina type of event,'' he said.

''In this time the eastern coast of Australia usually gets a lot wetter.''

La Nina occurs when there is warm water around Australia and colder water throughout the eastern Pacific Ocean.

Precipitation is then ''sucked in'' from the ocean, resulting in rain across the east of Australia.

La Nina's occur occasionally, usually around once a decade.

The last reported La Nina occurred in 1998-99, when 655mm and 599mm were recorded in Ballarat respectively.

The previous one was in 1989, which yielded 761mm.

''Sometimes they don't produce much, so in that sense we are quite blessed at the moment,'' Dr Stern said.

''But we can't say if the drought is over yet, we will just have to wait and see.''

''We should expect average amounts of rain in the coming months.''

Although Ballarat still requires an additional 229mm to reach the mean rainfall for the year of 692.8mm, which has not happened since 1996, Dr Stern said there was a good possibility 2010 would be a breakthrough year.