The annual summer travel rush is reaching its peak Thursday and Friday ahead of August 15, Greece’s major religious holiday, with thousands of travelers leaving Athens for the islands.

The ports of Piraeus, Rafina and Lavrio are seeing particularly heavy passenger traffic, while ferry occupancy rates have reached as high as 96% on some popular routes.

Among the most sought-after destinations are Tinos and Paros, which attract large numbers of visitors ahead of the August 15 celebration of the Dormition of the Virgin Mary, one of Greece’s major religious observances.

According to Greek public broadcaster ERT, 24 ferries are scheduled to depart from Piraeus on Thursday, August 13, for destinations in the Aegean Sea.

For the Saronic Gulf islands, 22 conventional ferries, along with 33 high-speed vessels and hydrofoils, are scheduled to operate.

Traffic is also heavy at other ports in the Attica region. Fifteen ships are expected to depart from Rafina, while nine are scheduled to leave from Lavrio.

Authorities are urging travelers to arrive at the ports early, particularly during the morning hours. Multiple departures are scheduled within short periods, which is expected to cause increased traffic at port entrances and on surrounding roads.