A severe thunderstorm watch is being issued for the Bay of Plenty region.

The MetService says an upper trough is expected to cross the North Island this afternoon and evening, generating very unstable conditions over northern and central parts of the North Island with scattered thunderstorms bringing localised heavy rain and hail.

"Between 3pm and 10pm today, a few of the thunderstorms could be SEVERE about Bay of Plenty, Rotorua, eastern Taupo, the ranges of Hawke's Bay and Gisborne, and Gisborne north of Tolaga Bay, with localised downpours of 25 to 40mm per hour and hail," says a spokesperson for the weather organisation.

"Rainfall of this intensity can cause surface and/or flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips.

"Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain.

"Any severe thunderstorms that develop will be isolated, and the thunderstorm activity should die away tonight."

Image: MetService.

For information on preparing for and keeping safe during a storm, see the Civil Defence Get Ready website.

A current state of emergency is in place for New Zealand following the devastating destruction left by Cyclone Gabrielle.

As the clean-up continues, people are warned to be prepared and not to take any chances.

If life, health or property is in danger, call 111 immediately.

• Keep up to date with MetService weather forecasts.
• Follow the advice of civil defence and emergency services. Self-evacuate if you feel unsafe.
• Have grab bags ready for everyone in your family. These should include short term essential supplies such as medications, snacks, water, torches, pet food, and baby formula (if needed).
• Remove any debris or loose items from around your property and tie down heavy outdoor objects. If you have a trampoline, turn it upside down to minimise the surface area exposed to wind.
• Clear debris and leaves from external drains and gutters to prevent overflow or water damage in heavy rain.
• Check on your neighbours and anyone who might need your help.
• Power cuts could affect EFTPOS and ATM machines, so make sure you have some cash at home or food and water to last 3 days.
• Visit the Get Ready website for more information about how to get ready for severe weather.