tldr: display mm/h or mm/3h, not mm.

Displaying “mm” as a unit of rainfall (accumulated or rate) does not make any sense, since the duration of measurement is an inherent component of this information.

You might reply that the duration is the duration between two data points (1 or 3 h).
I have two objections to that justifications:

1. we display wind speed in [distance/time] unit (kt). Using above justification, wind speed could be displayed in miles. Meaning either miles/h or miles/3h.
2. ambiguity exists in situations where the model jumps from 1h to 3h calculation periods. What is being displayed in the forecast? How should i compare data before and after the jump?

Therefore I propose to you to allways display rainfall rate in mm/h.

Re: Rainfall in mm