Usage of today() in range

I have a very simple measurement with only one field: temperature. What I want to do seems very simple: get max and min temperature of the day (since 00H00MN). I can’t figure out why the following query doesn’t work (it’s a query that I type in Grafana):

from(bucket:"hsohives")
|>range(start: today())
|> filter(fn: (r)=> r._measurement == "scale01temperature")
|> max()