A low pressure system that has moved across the south east of the state is responsible for the dip in temperatures and the spate of showers.
Weatherzone meteorologist Tom Hough said the cool spell will linger across the Mid North Coast through to the weekend.
Mr Hough says maximum temperatures for the week will hover around the 20 to 21 degree mark for the next five days while the minimum temperatures will linger around the 10 to 11 degrees.
"These temperatures are about the average long term maximum and minimums (temperatures) for May," Mr Hough said.
"Monday afternoon is likely to see a stronger chance of showers and this will be the trend for much of the week.
"In terms of showers, it will be mostly sunny on Tuesday, with showers forecast for Wednesday and Thursday before clearing on Friday.
We are expecting clearer skies on Friday and this will actually see the minimum temperature drop to around eight degrees.Tom Hough
"We are expecting clearer skies on Friday and this will actually see the minimum temperature drop to around eight degrees.
"There is also the chance of a few showers on the weekend, but it is too early in the week to predict that with any certainty."
Mr Hough said the showers will realise between one to five millimetres only.
And while you can rug up against the southerly winds, Mr Hough said it will feel 'a touch cooler than what it is'.
"The winds on Monday will be around 25 to 30 kilometres per hour and dropping to the mid-teens from Tuesday onwards," he said.
Off-shore conditions will see some significant wave heights of up to three to four metres on Monday before gradually easing to around two to three metres on Tuesday.
"By Wednesday those wave heights will drop to one to two metres," he added.