The Waikato Regional Council says it is likely to close State Highway Two through the Karangahake Gorge on the Coromandel Peninsula because heavy rain is causing rivers to rising
A slip in the gorge had already reduced the road to a single lane.
The council said temporary flood protection structures may also go up on the Criterion Bridge at Paeroa, stopping traffic getting into the town from Hamilton.
Motorists are being urged to avoid the area and to drive with care throughout the Waikato region.
Metservice said the worst of the weather was passing over Hamilton and making its way south.