WD for the Current Block.
I just double checked the block again, strange thing is that it uses the exact same code snippet, the exact same one, so the only thing I can think of is that the value was just changing. The current block is updating independently from your clientraw, whereas the Rain block just loads data from the db and does not update unless you refresh the page.
So what could happen is this:
Rain rate was 0.0
DB was updated
You loaded the homepage, Rain block shows 0
DB is updated again, rain rate is no longer 0
Current block updates in real-time and refreshes the value to the new one
Rain block only updates upon refresh - value stays at 0