Two words with a combined total of 25 letters, and what does it spell?
It means that the tram tracks in Berlin buckled due to the extreme heat. As a result the normal tram operation was replaced with bus service. It happened this weekend and it will certainly happen again.
I had never come across this phrase before and it certainly gave me pause. It will also give you an idea of what Berlin is dealing with in terms of weather at the moment!
Translating Berlin 
I grew up with much greater heat than this in SoCal, but somehow it seems worse here, even on days with 10% humidity. Did you see the news piece about the rescue in the ICE where the air conditioning system broke down. Temperatures over 50 °C and quite a number of people hospitalized. I’m fortunate to have access to an office in the south of Berlin which has air conditioning. I’m looking forward to my next visit there.