A severe thunderstorm watch has been issued for Northland, in addition to the heavy rain warning.

Northland, Auckland

Period: 15hrs from 7pm Sun, 29 Jan - 10am Mon, 30 Jan

Forecast: A slow-moving front drifting west should pass over northern Auckland and Northland this evening and during Monday morning. Thunderstorms are possible with this front, some of which may be SEVERE.

Regardless of whether thunderstorms occur or not, there is the possibility of downpours, with intensities of 20 to 40 mm per hour, especially between 7pm Sunday and 10am Monday, although conditions may ease slightly earlier in Auckland.

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.