The worst of Sydney's wettest and wildest couple of days in more than a decade may be over but minor flooding is likely to snarl the evening commute for many Sydneysiders.

The Bureau of Meteorology has already cancelled its severe weather warning for heavy rains and damaging winds for the Hunter region, and conditions are now easing for the metropolitan district.

"The threat has passed [for the Hunter region]," Sean Carsons, a senior forecaster at the Bureau of Meteorology said. "Sydney lies right on the edge of it."

"The main reason is that the low is just starting to weaken a bit," Mr Carsons said, predicting another couple of hours of showers for Sydney before skies start to clear.

Rainfall for Sydney reached about 225mm for the two days to 9am on Wednesday, the most in almost 18 years. Another 25mm have fallen since then. Winds to Sydney's north, such as at North Head, were the strongest on record, Mr Carsons said.

Weatherzone: Sydney radar

Even with the lighter winds and the odd patch of blue sky expected for Wednesday afternoon, the journey home for students and workers may still be a tedious one.

"It's the flash-flooding that's creating the commuter chaos. There's water that's half a metre deep on some of these roads under these showers," Mr Carsons said. "As these showers break down, maybe some of that water can drain away."

Sydney's western suburbs should receive clearing conditions by around 4pm, Weatherzone noted earlier on Wednesday.

The SES, meanwhile, is seeing little let-up in demand for its services, posting to Twitter this note not long before 1pm:

Our Operations Centre are experiencing extreme volumes of calls to the 132 500 number. There are more jobs than... http://t.co/NFONbxYOn9— NSW SES (@NSWSES) April 22, 2015

Sydney's near-term outlook will improve further on Thursday and Friday, helping the clean-up proceed.

"It will be a hell of a lot better than the last few days, that's for sure," Mr Carsons said, adding that rainfall in coming days will mostly be confined to state's far-south coast.

East coast lows

While another low pressure system may arrive over the weekend it is unlikely to develop into dangerous storms.

The low will probably bring cool, showery conditions for the state's south-east, with the Snowy Mountains possibly getting some snow. "At this stage we certainly don't expect any storms or severe weather coming towards coastal NSW,"  Mr Carsons said.

Brett Dutschke, a senior meteorologist with Weatherzone, said this week's east coast low had formed very rapidly in part because sea-surface temperatures in the Tasman have been one or two degrees above average for this time of year.

The current event will have churned up those waters, meaning "the next time we get a weather pattern conducive to an east coast low, it's not likely to develop as readily." he said.

While this weekend's approaching low is unlikely to re-intensify off the NSW coast, there is the chance of another low moving through late next week or the following weekend.

"At this stage it doesn't look like it's going to be intense," Mr Dutschke said.

The bureau's Mr Carsons said east coast lows are the most frequent at this time of year up until about June, but the near-term outlook is benign.

"I would say the next week or two look fairly settled in terms of weather, dominated by high pressure," he said.

Wind and rain

Agata Imielska, senior climatologist at the Bureau of Meteorology, has identified some of the records associated with this week's storm.

On the wind front, Newcastle Nobbys Head recorded 135 km/hr at 5am on Tuesday – the highest wind gust recorded for April at this site over the 48 years of data.

For any month of the year, the previous high for wind at Newcastle Nobbys Signal Station was 152 km/h on 23 June 1998, while the annual record is 170 km/h on 26 May 1974.

Norah Head also had 135 km/h at 4.44am on Tuesday, that's the highest or any month since 146 km/h was recorded on 5 March 2007. The site record only goes back 13 years.

Sydney Airport registered winds of 96 km/hr on Tuesday, matching a speed recorded on March 1 this year. For April, though, it was the strongest wind at the site since 1999.

Williamtown's RAAF base recorded 113 km/hr on Tuesday, the strongest for any month there since October 1999 and the strongest in April for 53 years.

On the rain side, Sydney's two-day total until 9am on Wednesday of 225.2mm was the highest in almost 18 years.

Branxton in the Hunter collected 369.4mm over the two days, a record for any month in data going back to 1863.

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