If you needed a few extra layers this morning, this is why. We're shivering through our coldest May morning in 18 years.

"Sydney has cooled down to 7 degrees this morning, which is the coldest May morning in 18 years, across the city, temps have plunged about 2 to 3 degrees colder than it has any other time this season" Rob Sharp from Weatherzone said.

While winter is on its way, the experts say it's a little bit unusual this early on. "This kind of morning is fairly typical of winter but it is fairly unusual to see it this early in the season" he said.

"In western suburbs this morning we've seen temps drop down to about freezing, so there's a fair bit of frost on the ground in a number of suburbs".

So the advice is, rug up, winter is coming!