A severe thunderstorm warning has been issued for parts of NSW to the north and east of Canberra.

The warning has been issued for places including Yass, Goulburn, the Southern and Central Tablelands and the Illawarra region.

The Bureau of Meteorology issued the warning about 1pm on Saturday, December 24. 

"We have a very dynamic situation currently," forecaster Steph Spackman said.

"We're expecting the thunderstorms to continue in the region mainly to the north and east of the ACT, and we're not expecting anything of severe nature over the ACT," she said.

"We will continue to monitor it closely throughout the afternoon and we will adjust the warning accordingly."

The State Emergency Service is advising people in areas likely to be affected by the weather warning to move cars away from trees, secure loose items around the house, keep away from and report fallen power lines, and keep clear of creeks, storm drains and flooded areas. 

For emergency help in floods and storms, contact the SES on 132 500