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.

Sunday will be another cloudy day, with a low chance of a storm teaming up with more showers.

But for mushroom hunters and those generally entranced by things fungal, the past few weeks have been bountiful.

Many mushroom species need four days of rain to get the signal "that it's time to start spreading the spore", resulting in the fruity stems pushing their way up, said Ray Kearney, a retired Sydney University professor and chairman of the Sydney Fungal Studies Group.

The emergence of different mushroom species starts from early autumn and lasts right through winter.

The many varieties - numbering in their thousands in Australia - are highly dependent on temperature and rain, he said.

Some species, though, should be admired at a distance given their spores can trigger allergies if inhaled. These include the common shell-shaped schizophyllum mushrooms found growing on tree trunks.

"People should not go out and pick mushrooms to eat unless they are absolutely sure of the species," Professor Kearney said.

"There are lookalikes [to some edible species] and some are highly toxic.

The saffron milk cap (Lactarius deliciosus) is one introduced species that is edible - and now being picked with abandon in pine forests near Sydney.

"Stems have a distinctive pattern of darker orange blotches, [and] when cut, the gills exude a carrot-coloured milky juice," Professor Kearney said. "When bruised or old, the surface becomes green."

Also common among the pine rows are the fly agaric mushrooms (known scientifically as Amanita muscaria). These resemble those found in fairy tale picture books with their bright red cap and white flakes - but are poisonous.

Along with the beauty, fungal species play a rich and extensive role in ecosystems, with all orchid species dependent on them, Professor Kearney said.

One orchid species even mimics the odour of mushrooms to lure fungi gnats to help it pollinate.

While ample rain helps trigger the abundance of mushrooms, too much will leave many waterlogged.

On that score, there is some better news ahead. The arrival of a cold front by late next week should help budge the persistent onshore winds that have fostered the persistent showers, Mr Brittain said.

Sydney should then enjoy fresher, less humid conditions with clearer skies - but temperatures should start to feel a bit more autumnal.

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