Severe thunderstorm for NSW

A dangerous thunderstorm is set to hit the Blue Mountains, Hawkesbury, Maitland and Cessnock areas of NSW.

Large hailstones, heavy rain and damaging winds are forecast as the storm moves through the Yengo National Park towards the state's northeast.

The Bureau of Meteorology issued a severe thunderstorm warning for the region shortly before 5pm on Wednesday, labelling the storm "very dangerous".

State Emergency Services advise people to move cars under cover, stay away from fallen power lines and keep clear of creeks and storm drains.