Setting an Outlook 2013 task recurrence hourly is not possible “out of the box”. If you want to set a task to reoccur hourly in Outlook the workaround would be to create separate daily tasks for each hour that you need to be reminded.

For example:

If you want to be reminded of a task at 8am, 9am and 10am each day you would need to set up three separate daily tasks:

Task 1 – Recurrence Daily at 8am

Task 2 – Recurrence Daily at 9am

Task 3 – Recurrence Daily at 10am