This is a hard question to answer because mirage is a variable. In general, mirage effect is like what happens when you stick a cleaning pole into a pool. As soon as the pole enters the water, it appears that the angle of entry changes (or the pole bends). If you have your rifle on a solid rest, and you look through the scope, mirage will make it appear that the crosshairs are dancing around on the target. Reading mirage is an art form that you are always learning.
Well, Yesterday, I was shooting at 300 yards and in wind for the first 100 yards of the shot. I was also shooting through mirage for my first time. I had a coupe of fliers and was trying to figure out what part of it was operator error what part was wind and what part was mirage.
Mirage will become your friend, once you pay your dues. Mostly because you can see it. It will flow with the wind and boil when the wind stops. Boiling is when mirage is always an enemy.
Next time you go out set the rifle solid with the reticle centered on the bull. Get off of the rifle but still look through the scope. Watch the bull dance around the reticle. Pretty interesting.
As the wind varies watch what the mirage does. Some one other than me should discuss the refraction as my shots always go opposite to where I desire if mirage is flowing different than when I take that first shot. It's enough to make a fella say some bad words. Also one reason I quit local bench rest competition. After one bad shot I could never get my act together.
I've seen mirage flow horizontal left, horizontal right, every thing in between and boil all in the time allotted for a 5 shot group and never settle to where it was when the first shot was made.
Regardless of scope power, mirage is still there, BTW...