When the mercury rises, and humidity is way up and the air is just plain junk, what changes should be made to an alcohol Animal?
Lean down the carb?
Lower the gear ratio (Larger sprocket)?
Ignition timing advance?
Just lean the carb .001" (generally main jet only.) You might get away with simply moving the clip on the needle up a notch or two in even the worst air. No major adjustments. Use an air density gauge and monitor just how much the density has changed moreso than temp and humidity. It all factors in, but I'm more concerned with the density altitude.
A simple a/d gauge (Kinsler, etc) will do a fine job, or you can get a bit more technical (and expensive) and use a Computech weather computer and really stay on top of things more accurately.