According to the Bureau of Meteorology, about half of NSW began experiencing a low-intensity heatwave from Monday that will strengthen through the week.

Weatherzone meteorologist Joel Pippard said the capital would have warm days and nights, with temperatures of 30 plus every day this week.

"Today we're looking at 30 degrees, which is actually the coolest day of the week, this week," Mr Pippard said.

He said the heatwave would begin on Wednesday and run to Saturday, which would be 34 degrees.

"It's classified as a low intensity heatwave, so generally speaking it's both days and nights that are usually five-degrees above average for at least three days in a row," he said.

Mr Pippard said it was pretty warm for this time of the year; 26 degrees was the average December temperature. He said the minimum average was 11.4 degrees. This week Tuesday and Wednesday had a forecast minimum of 14, the lowest of the week, with Thursday being the warmest day and night.

On Tuesday, temperatures would warm to 31 degrees, 34 on Wednesday before reaching 35 degrees on Thursday.

He said there was a chance of some showers, possibly a storm on Friday evening, but it was looking fairly dry until Monday week.

With two weeks to Christmas, Mr Pippard said it was too early to give a prediction, but at this stage it was looking like an average Canberra day.

"High-pressure usually means that it's clearer and there wont be a lack of clouds," he said.

"It's more likely for it to be dry than wet at this stage.

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