I wanted to comment on "sending extra air into the filter". Some automated backwash sequences have only an inch or two of freeboard at the end of the air/water step (the time when air scour is ramping down and water backwash is beginning). Extra air could send media over the troughs, resulting...
I have more of lab perspective: your operators are probably commenting on the effect temperature has on their particular test method. Check the Hach manual (if they are using Hach equipment) or "Standard Methods" if they are using one of those methods for temperature info. I have seen several...