Good morning,
Weekly Maintenances (Wednesdays in Europe) are posted on the BattleNet app., in-game, and on the support site.
As for maintenances that are done during the week (usually because we’re trying to fix something important, which can’t wait until the next Wednesday), these are posted a few hours before they happen, on the BattleNet app. A last minute warning is pushed in-game to warn players to log off, 15 minutes the servers go down.
This is how the Breaking News looked like this morning:
P.S.: we do not own or operate third party sites like MMO Champion, or Wowhead, so whatever they post on their site would be up to them. 