Storm warning issued as big wet returns

The Bureau of Meteorology has issued a thunderstorm warning for a wide area of central and eastern NSW, extending to the Sydney Metropolitan region.

"Severe thunderstorms in the warning area have temporaritly eased, further severe thunderstorms are still possible. The situation is being monitored and further detailed warnings will be issued as necessary," the bureau said just before 5pm.

Large hailstones and heavy rainfall that may lead to flash flooding are likely.

Locations across the state that may be affected include Sydney, Wollongong, Orange, Mudgee, Bathurst, Katoomba, Walgett, Dubbo, Parkes, Cobar, Bourke and Lightning Ridge, the bureau said.

"There's a high chance for showers each day" up until about the weekend, said Graeme Brittain, a Weatherzone meteorologist.

Storms are also possible on Wednesday afternoon, he said.

The additional moisture that's available has combined with upper-level pools of cool air to create ongoing instability and rain.

While nights have been exceptionally warm, the clouds are keeping a lid on temperatures - although most days are above the March average.

"There's no real sign of any real heat making it towards the coast over the next week or so," Mr Brittain said.

Still, there's a chance for some reasonable sunshine on Sunday and early next week, as temperatures in the city climb back towards 30 degrees.

So far in March, Sydney has had 18 days with at least 0.2 millimetres of rain, or well above the average of 13.6 rainy days for March, according to Agata Imielska, senior climatologist with the bureau in Sydney.

The record of 26 rainy days, set in 1870, is perhaps out of reach but the 22 wet days in March 2014 is within reach.

In terms of rain totals, the 223 millimetres is already well above the average of 129.6 millimetres for March at Observatory Hill.

"The record March total is 521.4 millimetres in 1942, so we've got a way to go to reach that record as well," Ms Imielska said.