Hi folks. Not sure how I missed this earlier but I just stumbled upon it. I think a big part of the issue is that we recently updated the blue bar and my statement from April 23rd is no longer accurate!
Prior to a recent app update, the y-axis indeed applied to both the blue bars (corresponding hourly rate for amount of rain collected in the time period shown) and the green line (daily accumulation).
However, as of about September 1, 2019 (depending on which app you’re using) the blue bar indicates the “descriptive” intensity of the rain (very light, light, moderate, heavy, very heavy, extreme).
What did we change the bars? Because so many people were confused by the “corresponding hourly rate for amount of rain collected in the time period shown” issue. The blue bars and green line now match what’s shown on the main UI: daily accumulation and relative rain intensity.
Of course, there is no perfect way to display rate, since it’s all relative. For some fun with rates, see this discussion about speed limits.
PS: Remember, the Smart Weather apps are purposely simple (aimed at the average user), but our data is wide open and as complicated as you want to make it. There are a bunch of third party app, many of which probably do a much better job of displaying the more detailed rate data. And (as @eric notes), you can always write your own!
PPS: We reserve the right to change the blue bars in the future!