Fast-moving storms to bring heavy rain and possible hail to St George and Sutherland Shire

Storms are set to develop over the west of Sydney before moving across the city in the early afternoon, Brett Dutschke, a meteorologist at Weatherzone, said.

"Thunderstorms are still likely to be in the area for people's commute at around 5pm but they will be most likely starting to ease off," Mr Dutschke said.

NSW to experience above-average temperatures with Sydney set to reach a top of 35 degrees on Wednesday, about 10 degrees higher than the March average.  

The thunderstorm is likely to be fairly fast moving with north-westerly wind gusts predicted and between four and 10 millimetres of rain to fall across the city.

"It will be notably windy this evening, particularly the around the coast," Mr Dutschke said.

The weather is set to ease during the night with a top of 24 degrees and partly cloudy conditions predicted on Thursday.

It comes after hailstones the size of 20-cent pieces fell across parts of Sydney's west and the Illawarra on Tuesday as severe thunderstorms hit.

The warm weather follows the city's third-hottest summer on record for both maximum and mean temperatures, trailing only 2016-17 and 1990-91, according to data from the Bureau of Meteorology.