Makgabutlane said there is a likelihood of snow in some inland areas down to 500m on Sunday and 400m on Monday.
"While it may be the last month of meteorological winter, rainy and snowy weather shows no signs of slowing down for Aotearoa.
"With this kind of weather pattern, things can change fast and I would suggest that people check the forecast regularly for changes."
Tuesday's forecast promises relief from the wet and cold conditions with a fine day of mild westerly breezes and a high of 15C.
Wednesday will be similar with a high of 16C forecast and it will remain warm on Thursday with a northwesterly change and showers forecast.
The overnight lows for the week will dip to 3C on Sunday increasing through the week to 8C on Thursday.
After a week of rainy days, Whanganui experienced its peak rainfall on Tuesday, August 3, when 18mm was recorded at Whanganui Airport.