Another sweltering night ahead for Illawarra residents as cloud holds heat in

On Wednesday night the temperature at Bellambi fell to 23 degrees by 8pm - but then continued to rise again, reaching 29.3 degrees by 6.30am on Thursday.

The long-term average minimum temperature for January is 19.1 degrees.

Meanwhile Albion Park reached a low of 22.9 degrees by 1am - almost four degrees above average - and Kiama got down to 22.3 degrees at 7am on Thursday, close to five degrees warmer than average.

Meteorologist Gabrielle Woodhouse from the Bureau of Meteorology said there was a broad area of heat across Australia that had arrived in the Illawarra, pushing temperatures up.

"Coupled with that is some fairly extensive high cloud, which means we can't cool down overnight," Ms Woodhouse said.

The bad news for Illawarra residents is that there is another night of stifling conditions ahead.

"Tonight's going to feel worse than last night... Very warm, very uncomfortable," Ms Woodhouse said on Thursday.

Wollongong is forecast to hit a low of 24 degrees overnight to Friday, while Albion Park and Kiama can both expect lows of 22 degrees.

Ms Woodhouse said it was possible that Bellambi and Port Kembla could experience one of their warmest January nights on record, but noted that these weather stations did not have a long history so the significance of this was limited.

There is relief on the horizon.

Ms Woodhouse said a cooler southerly change was due to hit the Illawarra on Friday, possibly from early afternoon.

This will send temperatures down and bring breezy conditions to the coast.

There were also some showers expected, Ms Woodhouse said, as well as a chance of a storm, although rainfall would be light.

Daytime temperatures across the Illawarra are expected to remain in the low to mid-20s on Saturday and Sunday.