"On Wednesday there will be warm air because the cloud will thicken. There's a few afternoon and evening showers but they're mainly about the ranges and it's generally a nice day to start off with."
Temperatures were also forecast to reach 29 degrees on Thursday with cloud and afternoon showers about the ranges.
"The winds do turn more south easterly for a time there and then on Friday you'll notice those showers become more frequent from the afternoon."
A weather feature starting on the west coast of the South Island, set to slowly move across the South Island, would push into the east coast of the North Island and bring wet weather to Hawke's Bay from Friday, she said.
"It's going to move quite slowly across the northern part of the South Island and that could bring some heavy falls into northern Canterbury and Malborough.
"As we go into Friday the weather feature moves away from the country but pushes the easterlies back and that's when Hawke's Bay could get some decent rainfall, but it's early days at this stage."
Ms Murray said anyone considering outdoor activities such as hiking or camping from Thursday night to Saturday should check the forecast as it was possible severe weather watches or warnings could be in force.
"There will probably be some heavy falls up in the ranges. The winds are quite easterly so it's an onshore flow that will bring rainfall to the region.
"It's just a heads-up at this stage. There are some heavy falls forecast for about the ranges and the confidence in those is quite good so it's just really pinpointing where the worst of the weather is that comes by."
On Saturday heavy rainfall would ease back to showers and conditions would be mostly cloudy with temperatures easing to 21 degrees in light of south easterly winds, she said.
The forecast for Sunday - also the annual Waimarama Beach Day - was looking cloudy with a chance of showers and potential to develop into a nicer day as the weekend drew nearer, Ms Murray said.