On February 25th at 3:00 am PST for NA, 2:00 UK time for EUW, and 3:00 CET for EUNE, servers will go down for maintenance and the 6.4 patch will be applied.
"On 02/25/16, starting at, 01:30 Pacific Time (09:30 UTC), ranked queues will be disabled in preparation for patch 6.4. At 03:00 Pacific time (11:00 UTC), 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."Be sure to check your particular servers status page for your region's specific 6.4 maintenance times:
I'll keep you updated as more information on what the patch contains and patch notes become available. In the mean time, feel free to check the [ 6.4 PBE content ] for a tentative look at what is coming in the patch!