People are being warned to prepare for thunderstorms this evening.

MetService weather radar has detected severe thunderstorms in the Waikato near Hamilton, Cambridge and Morrinsville.

"These severe thunderstorms are moving towards the northwest, and are expected to lie near Hamilton, Gordonton, Ohaupo, Matangi, Hamilton Airport, Eureka, Hoe-o-Tainui, and other areas of the Waikato.

"These thunderstorms are expected to be accompanied by torrential rain."

Torrential rain can cause surface and/or flash flooding about streams, gullies and urban areas, and make driving conditions extremely hazardous.

The MetService has issued a thunderstorm watch for Auckland, Waikato, Waitomo, Taumaranui, Bay of Plenty, Rotorua and Taupo.

The National Emergency Management Agency advises that as storms approach you should:
- Take shelter, preferably indoors away from windows;
- Avoid sheltering under trees, if outside;
- Get back to land, if outdoors on the water;
- Move cars under cover or away from trees;
- Secure any loose objects around your property;
- Check that drains and gutters are clear;
- Be ready to slow down or stop, if driving.
During and after the storm, you should also:
- Beware of fallen trees and power lines;
- Avoid streams and drains as you may be swept away in flash flooding.