Queensland’s capital copped 795 millimetres of rain – the city’s wettest week since records began in 1840 – when floods killed 13 people and damaged 18,000 homes and businesses across the state’s southeast in February and March.

There is a 70 per cent chance a third consecutive La Nina will bring above-average rainfall to eastern Australia this summer, the Bureau of Meteorology says.

Brisbane Lord Mayor Adrian Schrinner said sandbags will be available for residents to pick up over the next three weekends from depots in Zillmere, Newmarket, Morningside and Darra.

The wet season doesn’t usually start until late October, but he said council workers have already packed 150,000 sandbags, triple the standard stockpile.

“While we can’t prevent severe weather, we can be better prepared, and that’s particularly important given predictions of another season of severe La Nina conditions,” Schrinner said in a statement on Tuesday.

“So we’re stepping up how we help residents prepare by opening our depots for the next three weekends.

“Our super sandbag weekends will not only give residents the opportunity to have sandbags at the ready, they will give them the chance to learn from the experts how best to lay sandbags.”

The lord mayor is particularly concerned about the low-lying suburbs of Karana Downs, Archerfield, Sherwood, Toowong, Yeronga, Yeerongpilly, Chandler, Bracken Ridge and West End.

The BOM is due to publish its next La Nina forecast on Tuesday, and says the phenomenon has only occurred in three consecutive years three times since 1900.

The council’s move comes after the Liberal National Party mayor last week called for the state government to build more water supplies so dam operators wouldn’t need to worry about supplies when deciding to release water ahead of forecast floods.

Operators of Wivenhoe Dam, Brisbane’s main water supply, conducted a series of flood mitigation releases during the February-March deluge, which critics claim intensified flooding.

Water Minister Glenn Butcher brushed off the mayor’s concerns, saying water supply compartments of major dams were full, but the flood compartments were empty.

He said dam controllers needed to guarantee water supplies, and it was too early to know if flood releases will be needed this summer.

The government is still considering a report on its preparations and management of the floods handed to them by the state’s Inspector-General of Emergency Management last week.

Butcher said he hadn’t read the report, but suggested “there could be opportunities” to increase the capacity of flood compartments for some dams.