Thunderstorm to bring damaging winds, rain across the Illawarra

The mercury may hit the mid-30s by mid-afternoon Friday but Bureau of Meteorology (BOM) meteorologist Hugh McDowell says a sudden cold snap with damaging winds is likely.

"We've got a southerly change moving up the coast this afternoon, once that goes through it will be far colder for the rest of day and into tomorrow," he said on Friday.

"There's a chance of thunderstorms developing ahead of that southerly change and there's the possibility of severe winds and possible heavy rainfall as well which could lead to flash flooding."

Winds are expected to pick up from 35 to 50kmh on Friday afternoon before decreasing to 25-40kmh later in the evening.

Saturday will continue with cooler temperatures - the predicted high is just 22 degrees - with cloudy skies and high chances of a thunderstorm and showers in the morning. Winds are expected to blow southerly at 25 to 40kmh before dropping off by dawn.

A mostly sunny day is expected on Sunday, Mr McDowell said.

"It's going to warm up again on Sunday, we're looking at a high of 25 in Wollongong and 27 in Nowra and then similar temperatures mid-week," he said.

Mr McDowell said the fluctuating weather is pretty standard for summer in February, noting that "we often see these contrasts as cold air comes out from the Southern Ocean".