Workers who left home dressed for summery temperatures on Monday morning would have shivered through their afternoon commute home, as southerly winds cooled the region.
For most of Monday, the Illawarra sweltered through the hottest day this month.
At Albion Park the top temperature recorded was 36.2 at 2.16pm, while at Bellambi the mercury peaked at 34.8 degrees.
But just over an hour later, it began to cool off around the region, with strong south to south westerly winds helping Bellambi to drop below 20 degrees by 4pm.
The temperatures will stay on the cooler side for the rest of the week, with Tuesday weather forecast to range from 12 overnight to a top of 19 degrees.
Wednesday and Thursday will reach 21, according to the Bureau of Meteorology, while Friday is expected to be rainy and 24 degrees.
The weekend will be wet and cool, with a 90 per cent chance of rain and a top of just 17 degrees on Saturday.