The NRMA Insurance Wild Weather Tracker revealed over 26,500 claims for wild weather were made nationally, the majority in NSW, making this winter the state's worst for weather damage claims since 2016.

More than 60 percent of home insurance claims were attributed to weather, well above the 49 percent average.

Torrential rain that drenched the state in July, causing flooding, landslips and road closures, contributed to the spike in weather damage, the report said.

The Illawarra region was hit the hardest, accounting for 7 per cent of all claims in the state, followed by the Hunter Valley, the Central Coast and the Goulburn-Yass region.

The Bureau of Meteorology declared the third consecutive La Nina event this week, meaning Australians are likely to face yet another drenching this spring and summer.

A La Nina event, combined with a continuing negative Indian Ocean Dipole, is a sign Australia's east coast is at a higher risk of flooding.

NRMA Insurance Meteorologist Dr Bruce Buckley said the forecast for the months ahead is unseasonally severe, and households should prepare for wild weather.

"This is a rare coincidence of climate drivers that favour bursts of very heavy rainfall capable of producing flash and river flooding through spring and early summer," Dr Buckley said.

"The impacts of a changing climate means that wild weather can strike anywhere at anytime but taking a few small steps to both reduce our level of risk and prepare for how we will respond can make a big difference when it happens," he said.

He encouraged Australians to clean their gutters and downpipes in preparation for the weather ahead.

NSW State Emergency Services (SES) Commissioner Carlene York said dams are already full and rivers high across the state, and the promise of more rain comes with a "very real possibility of flooding".

The last time three back-to-back La Nina events were declared was more than 20 years ago, between 1998 and 2001, according to Bureau of Meteorology data.

Flooding was rife in the three-year period, and Sydney was hit with one of Australia's most costly natural disasters, the notorious Sydney hailstorm in April 1999.

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