On 14-03-2019 starting with 11:00 EEST ( 02:00 PDT/PST / 05:00 EDT/EST ) for 3 hours, we'll be updating WordPress to the latest version 5.1 on all production instances. During this time, the wp-admin can become inaccessible for brief periods of time while the new version is applied. The public sites will not be affected and they will work normally. For any inquiries during this time don't hesitate to contact us at email@example.com
We recommend you to test this new version on your development instance, as they have already been upgraded to the latest WP version. If you find any problems before the maintenance, please drop us an email at firstname.lastname@example.org
containing the Subject: "WP 5.1 upgrade problems"
More details about the new version of WordPress can be found at: https://wordpress.org/news/2019/02/betty/
Update: WordPress 5.1.1 is out meanwhile, therefore we'll update directly to 5.1.1. More details about this release here:https://wordpress.org/news/2019/03/wordpress-5-1-1-security-and-maintenance-release/