Severe to extreme heatwave conditions are forecast for the entire eastern NSW coastline on Thursday, Friday and Saturday.

In the ACT, a low-intensity heatwave is expected to pass over Monday and Tuesday, Weatherzone meteorologist Kim Westcott said.

From Tuesday to Thursday, a severe heatwave is expected to arrive, if not Canberra itself, to the north and east, she said.

From Thursday, Friday, Saturday, the heatwave returns to low-intensity.

"Canberra itself will experience, from [Monday] until Sunday the first, probably, about 30 degrees or more each day.

"The hottest day by far is going to be Thursday, at 35 degrees."

Those in the capital can expect warmish nights too; minimum temperatures are predicted above 18 degrees for much of the week, with the warmest nights those on Thursday and Friday, at 20 degrees.

On the coast, temperatures are forecast just as high. Batemans Bay temperatures are set to peak at 35 degrees on Thursday, cooling gradually to 26 on Sunday.

Ms Westcott said a severe heatwave is predicted for the south coast from Monday that may last until Friday. With long-term December averages at Batemans Bay hovering around the 24 degree mark, the hot week could be "quite uncomfortable" for those at the coast, Ms Westcott said.

A heatwave is called when there are three days of above average minimum and maximum temperatures for a particular location.

Possible showers are also forecast at Batemans Bay later in the week.

For Sydney, the western suburbs are expected to reach the highest temperatures in the final three days of the year, with the mercury tipped to climb into the 40s each day, according to the Bureau.