Hmm... is that another Biblical reference? Something about the flood? Or in this case, Flood?
The clouds are composed of (or at least maintained by) nanomachines. This is mentioned in both the director's commentary for "The Second Rennaisance" (and I'd like to point out that Mahiro Maeda worked closely with the Wachowskis), and the script book for The Matrix Revolutions.
If only there were some way to search for a text phrase...maybe using the internet or something. I'd call it...hmm...Internet Look-Up Library, or ILULZ for short (the Z is just to sex it up a bit for the punters). Now if only some massive tech company would implement my invention.
Did it, though?