Sydney broke its monthly rainfall average in 24 hours as rescue agencies turned their attention to the north of the state, which could be inundated with as much as 300mm of rain in the coming days.

The city sweltered through a humid day on Wednesday, with almost all weather stations across the city recording relative humidity that exceeded the monthly mean of 64 per cent. Sydney Observatory Hill recorded a relative humidity of 93 per cent, while Badgerys Creek recorded 97 per cent, Camden 83 per cent and Horsley Park 99 per cent.

In the 24 hours to 9am Wednesday, parts of Sydney topped the mean monthly average rainfall of 119.3mm, with Marrickville in the city’s inner west recording 176mm, making it the wettest place in the state. It was followed by Sydney Airport (139mm), Rose Bay (125mm) and North Ryde with (120mm).

Marrickville Golf Club general manager Michelle Vernon was in the clubhouse on Tuesday when it received 102mm of rain in an hour. Marrickville’s average February rainfall is 75 to 100 millimetres.

Ms Vernon and other club members were trapped in the clubhouse at the height of the downpour in the early afternoon, but said they had local beers to keep them going. While part of the first fairway flooded, the water eventually began to recede back into the Cooks River by 6pm.

“We all knew we’d get a wet day, we just didn’t expect it to be that heavy,” she said. “It’s not the worst event we have had... it’s not an unknown event, but it’s not a regular event.”

She added that while the course remained wet on Wednesday, it was still being used by a few golfers - and ducks.