March has not just been great weather for ducks; it's also been a boon for mushroom pickers.

Sydney has clocked up rain on all but four days this month. With showers a good chance for the remaining days of March, the city could match the record of 26 rainy March days set in 1870; so far, there have been 20.

Rainfall totals are already above 280 millimetres - or more than double the average - making it Sydney's wettest March in 33 years, the Bureau of Meteorology says.

Saturday is likely to bring "just fleeting showers, generally in the afternoon", Graeme Brittain, a meteorologist with Weatherzone, said.