my policy (and not wishing to impose this on anyone else) is to classify a run under the warmest applicable category. so, taking the highest temperature during the run. for those knife-edge cases where i start and it's 48F and rises to 53F, i only record that portion of the run that i think was at or below the 50F maximum qualifying temperature. i'm also silly and record using "actual" temperature rather than windchill. i guess that's because my routes usually include varying degrees of shelter from the wind, so when i'm blocked from the wind, there wouldn't be much extra chillage whereas when i come out of the trees and turn into that 25mph headwind on the prairie, it's a different story.
but, the most important criteria are to have fun and not hurt yourself.
Well the competition isn't an official one, it's not fair to everyone, there is no awards or anything so I think ballpark is close enough.
I'll include windchill if its significant and I am exposed to it (often times on the rail trail I don't experience much wind since it is somewhat sheltered in trees). Usually I just check the weatherbug app on the phone and use the 'feels like' temp. Sometimes I question it though. Today it reported 14 mph wind yet the feels like temp equaled the actual temp.
If you want to be technical, then one should include road surface temp. That might be even more important than air temp actually, and can vary quite a bit from air temp. I like to include that occasionally when I talk about a run on here but I don't factor it into the spreadsheet logs (I don't know how you would factor that in anyhow).
Also for others that might be doing this for the first time I suggest instead of using a running total on the spreadsheet, to type each run into the cell. It helps in case you forgot which ones you've included (well, at least if they vary in length), and also gives you and others the ability to see the length of runs you typically do.
And it's pretty easy, for example if you've made recent runs of 3, 5, 2, and 5 miles then in the cell type =3+5+2+5 instead of typing 15. In either case, 15 will be displayed. But if you click on the cell of the former method you will be able to see the individual runs.
As for me... we've had temps down to freezing for several days now. It warms up quickly but running before noon lately I've been able to start logging stuff in the 40-50 column. If I can work my weekly miles up to normal quickly, I should be able to beat last years numbers since I started out pretty hurt last year with a strained achilles from my October marathon.