Southern Europe is experiencing one of its worst wildfire seasons in two decades, with Spain among the hardest-hit countries.

Firefighters in Spain, Portugal and Greece battled ongoing wildfires Friday, an important religious holiday in all three countries, as persistent hot, dry conditions challenged efforts to contain the blazes.

Specially trained firefighting units from Bonn, Dusseldorf and three other cities set off from Bonn at midday on Sunday to help Spain combat its severe wildfires, according to the Bonn Fire Department.