By RNZ

Northland and Auckland are being warned to expect severe thunderstorms and heavy rainfall.

MetService says from this afternoon western parts of Northland and northwestern Auckland could experience up to 40mm of rain in one hour.

It could cause surface or flash flooding, especially for low-lying areas, or lead to slips.

The warning is active until 11pm tonight.

The severe weather marks the first day of autumn and the rest of the week is expected to turn cold for many across the country.

Niwa meteorologist Chris Brandolino said as the season officially changed the weather would shift rapidly.

He said warm and humid weather this week wouldn't last into the weekend, as cold weather barrels northward.

Severe Thunderstorm Watch issued https://t.co/dagOswZRMo pic.twitter.com/tqIPUTuf9q

— MetService Severe Weather Info (@MetServiceWARN) February 28, 2021