The MetService is warning of likely thunderstorms and heavy rain over central New Zealand, which could cause flash flooding and slips.
The storms are being driven by a mass of warm, humid air covering much of the country.
Downpours of 25mm to 40mm an hour are possible, particularly about the inland Nelson ranges, and MetService says this could cause streams and rivers to rise rapidly.
It also says driving conditions could be hazardous due to flooding and poor visibility.
