Heavy rain and strong winds are expected to put an end to the sunny spree in the Bay of Plenty come the middle of the week.

A we move into today, the MetService forecasts more cloud will be seen across the skies; northeasterly winds will pick up and some rain starts to fall around the southwest of the country.

“Wednesday and Thursday are the main risk period for severe weather and Heavy Rain Watches are already in force for western and northern parts of the South Island. It’s likely some of these will be upgraded to Orange Warnings and areas in the North Island may be added,” said MetService meteorologist Lewis Ferris.

This potentially severe weather is brought about by a low pressure system approaching from the Tasman Sea which drags some warm and humid air across our shores, said Ferris in the latest update from the MetService.

"While this does mean some warmer than average temperatures it also increases the chance of heavy rain as the system passes over. Strong northeasterly winds will also be seen before the rain arrives," said the MetService's update.

"The Bay of Plenty has been rather dry throughout September, especially Whakatāne which has had about 30 per cent of their average September rainfall.

"The prolonged and potentially heavy rain due from Wednesday night through Thursday could bring more rain to parts of the region than they’ve seen this month.

"While most of the North Island will be covered by the warm and humid air, there is some cold air being dragged across the southern half of the South Island.

"This means Thursday brings the risk of snow falling down to around 500 metres for inland Otago and southern parts of Canterbury. Prolonged rain is also possible around these areas and severe weather forecasts might be issued.

"It’s a good idea to stay up to date with the latest forecasts this week as the weather from Wednesday will be very different to now and severe weather may impact numerous regions."