(Bloomberg) -- Auckland is bracing for another rain deluge later Tuesday that threatens more surface flooding and land slips on ground already sodden after a record downpour.

New Zealand’s MetService is forecasting that a new weather system will strike the nation’s largest city from late afternoon and persist into Wednesday morning. It issued a red-category heavy rain warning, predicting thunder, gales and localized downpours of as much as 40 millimeters (1.6 inches) an hour.

“Our concern is that Auckland is really vulnerable to rain,” senior forecaster Georgina Griffiths told a media briefing in Auckland. “We’re completely saturated, our rivers are up, groundwaters are up. The rain can exacerbate flooding quite quickly.”

The city of 1.6 million people spent yesterday cleaning up after torrential weekend rain and flooding that disrupted travel, devastated homes and killed four people. The region is in a state of emergency after experiencing its wettest 24 hours on record over Friday evening and Saturday. 

The nation’s three biggest general insurance groups said they had received nearly 10,000 claims as of Monday, adding that it is too early to assess their likely costs.

Residents returning to work Tuesday after an Auckland public holiday Monday are being urged to travel only when necessary, and to consider working from home. Schools that were due to resume after the summer vacation will be closed until Feb. 7 following a directive from the Education Ministry aimed at reducing traffic flows.

While roads and other infrastructure are being brought back into service, officials urged caution. Slips will continue to affect rail and public bus services, they said. There is a warning that high winds could disrupt Tuesday evening travel on the city’s Harbour Bridge. 

Auckland has seen 38% of its annual rainfall this month alone, with January set to be its wettest month on record, the National Institute of Water and Atmospheric Research said. The weather reflects the impact of atmospheric rivers, which are thin jets of air that move moisture beyond the tropics, it said. 

A similar phenomenon caused a series of deluges in California from late December to early January, killing at least 17 people and flooding cities and towns.

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