As people prepare to celebrate New Zealand's first Matariki public holiday, motorists are being warned to prepare for heavy traffic.

It's expected that many people will be hitting the roads this afternoon to head to their holiday destination for the long weekend.

Waka Kotahi Transport Agency is prediction heavy traffic on the state highways in both the Bay of Plenty and Coromandel.

"Traffic is expected to be busy northbound through this SH25/Tairua from 2pm to 7pm," says a statement released by the roading agency this morning.

"Road users are advised to allow extra time for their journeys or consider travelling outside these periods. Please drive to the conditions."

Traffic congestion can also be expected on SH2, from Tauranga to Katikati and SH29 over the Kaimai Range.

People are advised to drive to the conditions and be as patient as possible.