I don't shoot a lot in high heat for a couple reasons it is uncomfortable, longer cooling times requiredand it is essentially useless in regards to my hunting. Here high heat = higher humidity, it has been my experience this knocks down the POI(shoots lower). If I shoot at this time or conditions I don't do any fine tuning. All things being equal(no oil in the bore, proper cooling, seating pressureand same load/powder) 70 toa few degress below freezingF I have had very little variance in POI. In terms of inlines and sub powders such as T7 or pyrodex once the mercury drops to double digits on the minus side I have experienced some variances usually aknock down or slight delay fire that usually results in shooter errors.

Of course like mentioned if you never varified that it was indeed now grouping 2" higher it could be your ML needs to be fouled or oil in the bore creating a presure spike. Though I assume you fired more than 1 shot as you mentioned re-zeroing or adjusting your scope.

In any regard the only and best practice is shoot your setup as you were hunting, basically trail and error in simulated practice sessions for conditions. This will give you thescoop on whatyour setup does inthe temperature/conditions variances you'll seeduring hunting.

For meit means Isight in +1"/100for my average conditions/situationsI'll see in October's ML seasoncome Nov or even December I expect to be zero'd at 100 on those cold days. Through trail and error I feel no need to touch the scope caps after final sight in, unless a equipment problem arises or I need a different zero.

Good Luck