“Es zieht” — There’s magic in the air in Germany, and if that air happens to be coming through your room from the outside, it can apprently make you very ill!
The German expression “Es zieht” (literally “it pulls”) expresses, on the surface of things, that there is a draft (Br. Eng. “draught” — related to the word “drag”) in the room.
What’s much more important is what the speaker is implying, namely all of the following:
“It is drafty.”
“I strongly believe that the fact that I am experiencing the sensation of wind indoors will make me sick even though there is no rational basis for my belief.”
“Close the window! It doesn’t matter how hot it is!”
Thankfully, this phenomenon is not quite as common in Berlin as in other regions of Germany where it is also becoming a belief of the past.
And to be fair, it is not a uniquely German thing that an indoor breeze can cause a cold, pain in the neck, back, and joints, infections of the eye lining, or bladder infections (even though an outdoor breeze is perfectly fine and pleasant). It is also a common belief in Eastern and Southeastern Europe that one should be shutting all the windows and doors even during a hot summer day to prevent some serious harm caused by the draft.