This is v3.118 on Android 9.
The Rain Viewer radar works up until about ten minutes in the past. So if I look at the map, it’ll show me rain, but if I tap on the clock icon next to the time and go to “now”, all the radar information vanishes from the map. If I move the “now line” back in time about ten minutes the radar information comes back.
I have the sense that amount of past involved is variable, but it’s difficult to be sure. On the basis of the Environment Canada radar, the “rain vanishing” is not on the basis of “in the last ten minutes it stopped raining”.