MetService has issued a heavy rain watch for Bay of Plenty and the west of the South Island.

"Unsettled conditions continue to affect parts of the country, with periods of heavy rain for Bay of Plenty and the west of the South Island," MetService said.

"Heavy rain watches are in force."

The heavy rain watch for the Bay of Plenty and east of Rotorua is expected to last 16 hours from 5pm today until 9am tomorrow, Monday, July 14.

The periods of heavy rain may have thunderstorms, and amounts of rainfall may approach warning criteria.

MetService said there is a moderate chance of upgrading the Heavy Rain Watch to a Warning.

Heavy rain is also expected for the ranges of the Westland District in the South Island for 17 hours until 3am Monday.

"Please stay up to date with the latest forecasts," MetService said.