Spokesman Matthias Deml says the immense size of the cathedral and its 10,000-sq. metres of towering windows make it impossible to heat. The air inside is only a few degrees warmer than outside.

Cologne and the rest of Germany has been stung by frigid weather and temperatures remained below freezing on Thursday.

While services during the week are held in a heated chapel, Sunday's main mass is to take place as scheduled in the nave with its 43-metre -high ceilings. Deml says churchgoers are advised to dress warmly. -- AP