"There will be strong south-westerly winds, which at some point might reach gale conditions. It is looking like a very cold weekend."
Mr Mercer said on Saturday the high would be 15C but the overnight low would drop to 2C.
"It is a night for staying by the fire as we are expecting it to be very, very cold."
On Sunday conditions should start to ease but a south-westerly flow was expected to hang around until Monday.
Mr Mercer said it would still be cold overnight on Sunday with a low of just 3C.
"Although you're not getting as cold as places down south it will still be pretty chilly compared to what your used to."
However, the days leading up to this Antarctic blast were expected to be tropical in comparison, with temperatures reaching the high teens tomorrow and low 20s on Thursday.
A high of 19C was forecast for Napier and a high of 18C was forecast for Hastings.
Meanwhile, a high of 21C was forecast for Hastings and a high of 22C for Napier was forecast on Thursday.
Tomorrow was expected to have gusty northerlies and periods of rain but these were expected to clear in the evening.
"It will be mainly fine on Thursday but on Friday there is the chance of showers in the morning with falls heavy in some areas."
"Saturday is looking like the worst day of the week for Hawke's Bay as your caught in this south-westerly flow."
Mr Mercer said it was likely warnings and watches could be released but it was too early to tell at this stage.
"I think at this stage for Hawke's Bay the wind could be something to worry about rather than the rain although there could be some heavy falls."
