A heavy rain watch has been issued for parts of the Bay of Plenty and Rotorua, with forecasters warning conditions could worsen over the next two days.

In its latest weather update, the MetService said periods of heavy rain were forecast for areas west of Whakatāne, including Rotorua, from 3pm Tuesday until 6pm Wednesday.

Rainfall totals may exceed warning thresholds, with a high chance the watch could be upgraded to a heavy rain warning.

MetService warned that streams and rivers could rise rapidly, with surface flooding, slips and hazardous driving conditions possible during the period.

Residents were urged to prepare by clearing drains and gutters, avoiding low-lying areas, and driving with caution, particularly during heavy downpours.