Make sure to keep your coats and umbrellas handy on Sunday as the MetService has issued a severe weather warning for the Bay of Plenty.

A deep low is forecast to cross the upper South Island during Sunday, preceded by an active front which is expected to cross much of the country overnight Saturday and Sunday morning.

In the Bay, the MetService says rain is expected to become heavy early Sunday morning then ease from the west around 12pm.

'In the 12 hours from 2am to 2pm Sunday, expect 80 to 100mm about the ranges, especially east of Whakatane, with 50mm likely about lower lying areas.

'People in these areas are advised to watch out for rapidly rising rivers and streams and possible slips and surface flooding.”

Gales are also expected over much of the country with the passage of the deep low.

Keep up to date with the latest forecasts and any watches/warnings at metservice.com or on mobile devices at m.metservice.com.

You can also follow updates on MetService TV, on Facebook, @metservice and @MetServiceWARN on Twitter and at blog.metservice.com