Santa and his reindeer may be used to the North Pole's sub-zero temperatures and frosty winds, but it seems they will still have their work cut out in the Illawarra on Wednesday night.

Slippery roofs will be a likely hazard, with showers and possible thunderstorms predicted throughout the region on both Tuesday and Wednesday afternoons.

Rudolph's shining red nose will also come in handy as the cloudy, wet weather carries through to Christmas Day.

In Wollongong, temperatures will linger between 20 and 24 degrees early in the week, before reaching a mild 25 on Thursday.

Temperatures will follow a similar pattern in Bellambi, while the mercury should hit 27 degrees in Albion Park on Christmas Day.

Boxing Day is expected to remain cool and rainy, with showers likely across the region.

The rain is expected to clear by Saturday.