The differences have to be somewhat extreme for you to actually notice since you are an observer & not in the plane. I have seen degraded performance from engines and the model, most noticable during manuevers & landings.the less dense air affects the lifting power as well as the engine output just when you need it most.since warm air carries more moisture than cold air, the high humidity only ads to the problem. its well known in the full scale world airplanes fly better in the winter.

Hi I fly in south FL. ( palm beach county) It was 92F. at ourv field. With 90% humidity.
You need to adjust the needle valve a little rich of peak. If not sure your best bet it
to learn to use a Tach. Then you can peak the engine and richen about 200-300 less
than peak. we fly on 15% nitro as a standard for most engines. Both 2 and 4 stroke.
An engine in good shape can be adjusted to compensate for weather, we drink a lotof water and keep our heads covered. best, [email protected]

cool dry air is a perfect combination for an engine to run its peak,due to so many different conditions and elevations i think a slightly rich mixture would be a good all around setting.if you adjust your carburetor settings on a fair day you should expect not to have to mess with them much.i seldom have to readjust most of the motors i use.and i have one of almost everything.

Here is a suggestion (which I have never tried). On a hot, humid, high altitude day, your engine actually needs to run leaner to get the proper proportion of oxygen vs methanol. But it is hot and your engine needs to run cooler. So how about adding a couple ounces of oil to a gallon of fuel and leaving the needle alone? That would give you a little leaner mixture which ought to run a little cooler. You might have to fiddle with the proportions a little to get it right.