User Configuration > Administrative Templates > Microsoft Outlook 2016 > Outlook Options > Preferences > Calendar Options
User
HKCU\software\policies\microsoft\office\16.0\outlook\options\calendar
This policy setting allows you to set the update frequency (in minutes) for the Weather Bar. If you enable this policy setting, Outlook sets the update frequency to the specified value. If you disable or do not configure this policy setting, Outlook uses the default value of 120 minutes.