Please reference links below to view historical weather averages at each of the main stops on your pilgrimage.
Note: The most popular time to travel to Greece is during the spring and fall while avoiding the hot summer months. April, May, September & October are typically the best months to travel.
Thessaloniki
https://www.timeanddate.com/weather/greece/thessaloniki/climate
Kalambaka
https://www.timeanddate.com/weather/@261601/climate
Delphi
https://www.timeanddate.com/weather/@11287748/climate
Athens