I don't know if ERA5 data has some weird format, as I'm really not familiar with working with such data directly. But it's vital to realize that the greatest hourly temp is rarely the daily max, and the same idea with mins. Orlando's data today:
The max today was 87°F and the min 63°F (found from this using the 6 hour max\mins... there can be rare issues with this when those don't fall at midnight... station reports or metars give 24 hour max\min midnight to midnight... though it's only an issue when a max or min is near midnight, which is rare, typically only during airmass changes)
Whereas the top hourly was 86°F and the bottom one was 65°F. And that's a fairly typical thing to occur... they only match when the extreme temperatures happen to occur near the end of the hour (values are typically taken about 7 minutes before the hour in the US, and I believe that standard varies a bit internationally)
So I'd certainly question any work that tried to derive daily actual max\min values or compare to them using such hourly results, unless it turns out ERA5 does something unique. It's tough to imagine it's valid given it you only get one hourly value.
Precipitation measurements on the other hand are over a time period, so those values should be hourly values, and summing them should give the results for the day.
When it comes to temperature (assuming ERA5 isn't somehow strangely taking care of the discontinuity), you could try to apply some sort of rough multiplier to give a very crude better guess... but thinking you won't be able to get legitimate daily max\mins without looking for actual site data, which are for example available here for basic US historic or recent data searches, or at NCDC. Of course those are only going to work for places they have observation sites. But it doesn't seem that you can directly compare the ERA5 maxima results to actual station maxima easily.