All Interislander sailings have been cancelled tomorrow, due to forecast high winds and large swells.

Four Interislander sailings between Wellington and Picton were cancelled due to a forecast southerly weather system in Cook Strait.

Interislander said the safety of passengers and crew was its top priority.

"All affected passengers are being moved to alternative sailings and are being contacted directly."

Bluebridge has not yet cancelled its sailings but said if the predicted swells did eventuate it may have to delay or cancel services on Tuesday and Wednesday.

"We are monitoring the situation closely and if your sailing is impacted, we will notify you via text and email at the earliest opportunity," it said.