A classic southerly buster is in store for the Illawarra on Monday afternoon, as winds swing around and turn gusty and temperatures take a dive.
The region has already had its warmest day this month, with the mercury climbing past 30 degrees soon after 10am.
Showers and a possible thunderstorm will precede a cool change, Jacob Cronje, a senior meteorologist with Weatherzone, said.
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"People are calling it a southerly buster," Mr Cronje said. "It's going to be quite gusty."
Apart from Friday, when a top of 24 degrees is expected by the Bureau of Meteorology for the city, most days this week will feel on the cool side. Tuesday's forecast is for 19 degrees after an overnight low of 13 degrees.
"The air mass that will linger over the south-east [of Australia] is extremely cold for this time of year," Mr Cronje said.
Those cooler conditions are likely to bring about a welcomed easing of fire risks.
Today, though, could be a trying one for fire authorities, with total fire bans in place in the Greater Hunter, northern slopes and north-western fire districts.
The bureau has also issued a "fire weather warning" for those regions.
For Sydney and five other regions of eastern NSW, the fire risk today is "very high", the Rural Fire Service says.
While eastern parts of the state and Sydney received good falls at the end last year, the past dry spell - including the city's record stretch of days with less than 2 millimetres of rain - has meant soil moisture levels remain well below average in many areas, Mr Cronje said.
Weatherzone is owned by Fairfax Media, publisher of this website.