The La Nina that was declared in September, which brings with it increased chance of rainfall across eastern Australia, including Tasmania, is likely to be short and sharp.

In its La Nina and climate drivers update released on Tuesday, BOM manager of climate operations Andrew Watkins said this year's La Nina was likely to be less severe than in 2010-12.

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"This one may be short and sharp," Dr Watkins said.

The 2010-12 event resulted in the wettest two years on record for Australia causing widespread flooding and severe tropical cyclones.

Despite the increase chance of rainfall, Dr Watkins said it was unlikely to experience wet weather throughout summer.

"What we typically see is surges of wet weather activity, more frequently," he said.

"So we'll see increased rainfall events that will then fade to normal summer temperatures."

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BOM first issued a La Nina alert in August, which was upgraded to an "active event" in September.

La Nina events have the potential to impact agricultural activity, such as harvest time for vulnerable fruit and vegetables.

It can also damage fruit such as cherries, that require sunlight to ripen, but can be susceptible to wet weather events and split.

Dr Watkins said the impact of La Nina would likely not be known until after it was complete, saying impacts often showed up a few months afterwards.

BOM releases a climate drivers and La Nina update each Tuesday.