The aid flotilla organized by Greta Thunberg had to return to port shortly after it embarked on its journey to Gaza, due to encountering stormy weather, according to organizers on Monday.

The 22-year-old environmental activist was aboard one of the 20 vessels that departed from Barcelona on Sunday, in what they described as the “largest solidarity mission” ever. Meanwhile, Israel had threatened severe “terrorist-level” consequences, including her potential arrest.

But storms bringing 35 mph winds soon forced Thunberg and her pals — who also included “Game of Thrones” actor Liam Cunningham — to turn back.

The Global Sumud Flotilla Mission stated that they performed a sea trial and returned to port to let the storm pass, delaying their departure to avert complications with the smaller boats. The statement did not specify when the voyage would be rescheduled.

The Swedish climate activist set sail just months after she was detained when the Israeli navy detained a previous flotilla heading to Gaza.

Israel was again waiting to intercept the latest flotilla, this time with a plan to detain activists in harsh “terrorist-level” conditions in detention centers, Israeli newspaper Israel Hayom reported.

Israeli Prime Minister Benjamin Netanyahu has dismissed attempts to deliver food and humanitarian supplies to Gaza as a propaganda stunt in support of Hamas.

Israel also mocked the aid mission as being nothing more than a publicity-seeking “selfie yacht.”

Before her departure Sunday, Thunberg claimed her flotilla was “part of a global uprising of people standing up” to “atrocities” in Gaza.

Others included the former mayor of Barcelona Ada Colau, with Susan Sarandon a high-profile supporter.

The flotilla was set to be joined later this week by dozens more ships from other Mediterranean ports, including in Tunisia and Italy.

With Post wires.