Authorities in Greece are closing the Acropolis in Athens for a second afternoon on Thursday as the country swelters in unseasonably high temperatures.

The Culture Ministry said the hilltop citadel, which is Greece’s most popular ancient site, will be closed from midday to 5pm (0900-1400 GMT) because of the heat.

All other archaeological sites in the Greek capital will be closed during the same hours.

People who have booked visits for that period can use their tickets later in the day, the ministry said.

Temperatures are expected to exceed 40C (104F) on Thursday in much of central and southern Greece, including greater Athens, the Cyclades islands and Crete.

Officials are on heightened alert for wildfires, which plague Greece every summer.

The minister responsible for civil protection, Vassilis Kikilias, said Thursday posed a particular wildfire risk due to the combination of high temperatures and winds.

“The early start of the heatwaves, combined with the dry winter, has led to a very difficult fire season,” he said.

The fire service also warned of a very high wildfire threat on Friday.

Authorities in Athens are providing air-conditioned areas for the public and have issued fans to secondary schools where end-of-year and university entrance exams are being held.

Cooler temperatures are expected on Friday and Saturday.