The server itself isn't being touched, it's just network connectivity to it that might drop. Here's the full email for those of you who care:
Start: 2017-02-23 22:00 UTC
End: 2017-02-24 06:00 UTC
During the above window, we will be performing an upgrade of networking software throughout a segment of our LON1 region.
During the maintenance window Droplets in the region will lose networking connectivity for a period of up to five minutes. We expect the actual disruption to be minimal for most Droplets, but will be closely monitoring the region throughout the window.
Do not hesitate to contact support if you have any additional questions or concerns, you may do so by opening a ticket, or replying to this email.