Where thunder is thunder
When it's a big truck rumbling over a bridge or roadway. When it's someone in the apartment upstairs moving furniture. When it's a radio blasting with thumping bass, or a movie soundtrack turned up high so the dialogue is audible. When it's a faraway train. When it's a plane overhead. When it's a loaded dolly rolling over a tiled floor. I'm sure you could add to my list.
None of these options really exist here. Unlike at home, where there are many candidates for noisemaking, here, if I hear a boom or distant rumble, odds are, it's thunder.