Storm expected to intensify overnight
Civil Defence co-ordinator Bill Hutchinson says they were keeping an eye on river levels in Kaitiaia.
He says high tide would come at about 10.30pm-11pm, and said there could be potential for surface flooding.
Civil Defence has activated its emergency operations centre for the Coromandel Peninsula.
Thames Valley Civil Defence controller Garry Towler says the weather was likely to bring slips, downed trees and flooding in low-lying areas.
"It’s going to be a short, sharp and nasty storm and people need to be prepared."