Sydney could experience up to 100 millimetres of rain on Saturday, as a coastal trough stops the sun from breaking through the clouds until next week.

Showers are forecast to continue from Thursday into the weekend, the Bureau of Meteorology says, with 15-40 millimetres expected on Thursday, 35-80 millimetres on Friday and 60-100 millimetres on Saturday.

Thunderstorms are “definitely a possibility”, particularly on Saturday, bureau meteorologist Melody Sturm said.

“It all depends on the hit-and-miss nature of thunderstorms, if they move right across the area or if they will actually miss us, and go into the Hunter or the Illawarra,” she said.

The three-day burst of rain from Thursday is likely to be the wettest since at least last July when more than 130 millimetres fell over a similar period.

The totals, though, are unlikely to near the deluge in February last year when about a third of a metre fell over Sydney in four days, effectively extinguishing the bushfires that had scorched millions of hectares across the state in the previous half year.

“We do have a fairly wet weather pattern ahead of us, we’re already in it,” Ms Sturm said. “Definitely be prepared for the rain, it’s coming, potentially it could be more than what we’re used to.”

She said a coastal trough over the Sydney Basin area was going to “enhance a lot of rainfall”.

Weatherzone meteorologist Ben Domensino said the country would experience “widespread rain over parts of every state and territory during the next eight days”.