Have a page with a table of recent values http://silveracorn.co.nz/weather/wxcutrends.php (of course by the time you look at this the values may will have changed).
It is showing 58.0 mm rain for 18 and 24 hours ago. 58mm was the total for the day (50.2 the day before!) and its spring!
However $r24hours is zero as the last rain tip was just over 26 hours ago.
It appears the tag <#RecentRainToday h=18> is reflecting what the graph shows - i.e. as the graph continues with the total for the 'day so far' it continues to retain the maximum value for the day until the daily rollover. It seems the tag is doing the same thing which was not expected. Is this the way it is supposed to be?
I have tried using minutes in the tag instead of hours but the result is the same (as expected) but you never know - worth a try
It seems only rain is affected in this way, which I presume is because only rain maintains a running total for the day.