A weather system that exacerbates drought and bushfire conditions is set to hang around longer than usual, the Bureau of Meteorology warns.

The strong positive Indian Ocean Dipole (IOD), which usually brings reduced rainfall and higher temperatures for much of Australia, has weakened slightly in recent weeks from previously record levels.

However, an update from the bureau today says the weather system is “likely to be slower to decline than usual, and may persist into mid-summer”.

“Positive IOD events are often associated with a more severe fire season for southeast Australia,” it says.

Insured losses from the NSW and Queensland bushfires, which have been declared an insurance catastrophe, have increased to $165 million from 1525 claims lodged with insurers, according to the Insurance Council of Australia.

The losses are expected to rise further, with emergency crews still working to contain dozens of new bushfires in the two states.