The Bureau of Meteorology says there is a 50% chance a La Nina weather system will develop later this year, bringing with it above-average rainfall and the prospect of floods.

The current El Nino continues to weaken, with Pacific Ocean temperatures falling fast, and the likelihood is increasing of it moving straight into the opposite La Nina effect.

While El Nino generally brings drier, warmer conditions to Australia, La Nina is associated with much higher catastrophe losses for insurers.

Five out of eight surveyed models suggest a La Nina is likely, with three neutral, while continuing record Indian Ocean warmth is expected to provide extra moisture for rain systems crossing Australia in the autumn.

However, the bureau warns forecasts at this time of year can be inaccurate, with a clearer picture likely to emerge in coming months.