I received this ten days ago:
As part of our ongoing commitment to performance, reliability, and security, we sometimes perform maintenance operations in our Microsoft Azure regions and datacenters.
We want to notify you of an upcoming maintenance operation. We will be performing maintenance on our networking hardware. We are scheduling the update to occur during nonbusiness hours as much as possible, in each maintenance region. Single and multi-instance Virtual Machines and Cloud Services deployments will reboot once during this maintenance operation. Each instance reboot should last 30 to 45 minutes.
The following are the planned start times, provided in both Universal Time Coordinated (UTC) and United States Pacific Daylight Time (PDT). The maintenance will be split into two windows and will impact Virtual Machines or Cloud Services in either half of the maintenance. We expect each half of the maintenance to finish within 12 hours of the start time.
The maintenance period was from the 15th to the 17th August, so it looks as though they managed to stuff it up some how...