He said that was down to warmer air being brought from the north - as opposed to colder air from the south - and also wind generally warms up as it comes over the ranges into Hawke's Bay.
"You have wind coming over the ranges and as it comes over the ranges and descends it warms up."
Temperatures will reach a high of around 17C in areas like Napier, Hastings and Wairoa on Monday and Tuesday and slightly lower in areas like Waipukurau.
Rain could arrive in the region on Wednesday for a spell, followed by heavy winds on Thursday, and a possible change to southerlies on Friday or Saturday - which will bring colder temperatures again.
"We will see the southerlies come back," McInnes said.
"That will make things a bit cloudy and a bit damp and a bit colder unfortunately."