"There were thunderstorms out to sea and people living in coastal areas would have noticed them."
Makgabutlane said 16.2m of rain was recorded in Whanganui over 12 hours on Saturday night and Sunday morning.
"There was a bit more in some parts of the region and Whanganui can expect more from a second front which could bring hail.
"It is likely to turn westerly and the winds will still be quite strong although there are no warnings in place for the region."
Showers are forecast throughout Monday and a strong southwesterly with more rain is forecast for Tuesday. The winds are likely to die out in the evening before a cloudy day on Wednesday. Clear skies are expected to return on Thursday.
Temperatures for the week are expected to range from a low of 4C overnight on Tuesday to a high of 20C forecast for next Sunday.