Server maintenance for patch 3.8 has been scheduled for 3:00 PDT for NA, 2:00 GMT for EUNE, and 5:00 GMT for EUW.
Here is the Riot NOC announcement from the EUW forums:
"On 12/06/13, starting at 03:30 GMT, ranked queues will be disabled in preparation for patch 3.8. At 05:00 GMT, 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 6 hours."
If you are wondering what will be included in the patch, check out the 3.8 patch notes and patch preview here.