Friday was set to be the wettest day of the week, but Best said the rain wouldn't necessarily be consistent and shouldn't affect the entire day.
"We'll still have a partly cloudy start to the day, and there will be a few showers around the end of the morning and moving into the afternoon, and westerlies will start to turn southerly by the end of the day."
Looking ahead towards the weekend, Saturday might be slightly wet, but Sunday was looking decent.
"There will be one or two early showers on Saturday, those southerlies will gradually die out, with the temperature a little bit cooler at 18C.
"The good news is Sunday is fine with westerly winds, with a maximum temperature of 19C."
For today, Whanganui is looking at a high of 17C, with an overnight low of 6C.