Maritime New Zealand's Rescue Coordination Centre and the Coastguard are conducting a flare training exercise in the Whangārei Harbour on Tuesday night.
Residents in the Snake Bank area should expect to see several red and orange-coloured distress flares and some smoke flares in the night sky from 7-9pm, police said.
Police were asking the public not to call emergency services if they saw such flares in the area between those times.