Rain is expected in Whanganui from Tuesday onwards but MetService is still predicting a dry Christmas Day.
MetService meteorologist Lewis Ferris said a low pressure system was forming in the Tasman Sea.
"That's going to wrap around the country around that Wednesday and Thursday period, and it's looking like it'll bring some wet weather to Whanganui on both those days.
"On Tuesday there'll be bits and pieces of rain throughout the day, more likely in the afternoon hours. The rain will get more substantial as we go into Wednesday.
"It'll be pretty breezy on Wednesday and Thursday as well from that north-northwest direction."
While it would remain "relatively wet" up until Thursday evening, Ferris said winds would turn around to the southwest overnight and "things should clear up around the region".
"There's the chance of an early shower on Friday morning, then fine spells with temperatures of 20C. The westerly winds will be slowly dying out through the day.
"The low will be moving pretty quickly across the country and away to the east, but at this point it looks like there could be a little more wet weather on the cards for Boxing Day (Saturday)."
Temperatures would remain at around 23-24C through to Thursday, Ferris said.
"The most intense rain this week is expected to move through pretty quickly. It will be heavy for a time, but at this point it's not looking like we'll reach any warning criteria.
"Things could be a lot worse."