Students living in a small number of low-lying flats in north Dunedin are warned to prepare for a possible evacuation, as heavy rain continues

Otago University's Campus Watch is door-knocking about 20 affected homes, located between Montgomery Avenue and Leith Street.

They're advising residents of possible flooding if the stream the Water of Leith, overtops later tonight.

Those choosing to remain must have a bag packed, and emergency services will evacuate residents if necessary, later tonight.

In other areas, Clutha District Council is expecting surface flooding, as a heavy rain watch remains in place until 1pm tomorrow.

Severe weather is also expected to close several north Otago highways tonight.