St. Athanasios of Paros records the following miracle of St. Paraskevi which took place in 1442 on the island of Chios which is annually commemorated on October 14th:
A hieromonk named Ambrose was celebrating Vespers in honor of Sts. Nazarius, Gervasius, Protasius and Celsus in the Church of St Paraskevi on October 14th in Palaiokastro in the village of Halandra. No one else was in the church. At the end of the service, rain suddenly began to pour down in torrents with a great roar as if the sea was being emptied onto the island, and this continued all night. Ambrose was unable to leave the church and return to his cell. Thinking that the island would be completely flooded by the storm, he began to pray to God to save his homeland and soothe His righteous anger. [St. Athanasios interprets this storm as a consequence of the aftermath of what happened at the Council of Ferrara-Florence.]
The pious hieromonk Ambrose prayed for hours to the point where he grew tired and sat down at a stasidi. While sitting he fell asleep. He had a dream at dawn and saw the church roofless, and, in the heights, a cloud of light within which stood the form of a beautiful and modest woman in prayer to God with hands raised. After her prayer, she said to the Ambrose who was struck with fear: "Ambrose, don't be afraid; I am the Righteous Martyr Paraskevi; your homeland is saved." Ambrose immediately awoke and noticed the rain stopped at once. With joy he began to pray the Matins service.
People from the lower village came up and informed Fr. Ambrose that the waters from the sea rose up to their part of the village up to the Church of Panagia Eleimonitria. It was at that time that Fr. Ambrose revealed to them his vision of St. Paraskevi and her promise that the island was saved. Taking her icon he proceeded to the flooded area of the island and lead a litany. When this was done the waters receded back to the sea. For this the people glorified God for the miracle worked through the Virgin Martyr Paraskevi.
From that time, the island of Chios has celebrated St. Paraskevi's feast day with great solemnity, primarily on her feast day on July 26th, but also on October 14th to celebrate her great miracle. Till this day her holy icon works miracles for the people of Chios.
For the hymns on this feast, see here.
The text of St. Athanasios of Paros can be read below: