While last week brought the first true heatwave of the summer, the Bureau of Meteorology has no doubt put a dampener on many Christmas plans by predicting a mild December 25 for the Illawarra, punctuated by possible showers.

The mercury will climb to just 23 degrees in Wollongong and 24 in Nowra, according to BOM forecasts, with showers likely to hang around for the rest of the week.

Temperatures will climb towards a more summer-like 29 degrees in Wollongong on Saturday, while Nowra residents should dust off the swimmers with 32 degrees expected over the weekend.