Here is Riot Rival with the NA maintenance announcement:
On 07/10/13, starting at 01:30 PST, ranked queues will be disabled in preparation for patch 3.9. At 03:00 PST, the servers will be shut down and all games currently in progress will end in a draw and stats will not be recorded. We estimate the battlegrounds will be unavailable for 3 hours."
This patch will contain Spirit Guard Udyr and the numerous balance changes currently on the PBE. It will not contain the Master Yi visual update or Lucian.