Originally Posted by
GordonR_Cape
The maximum water vapour content of the atmosphere at sea level is 4%, which puts an upper imit on the correction factors in the density formula.
Anecdotal reports of temperatures of 37C/100F and 100% humidity should be disregarded.
4% specific humidity is ~1.5% density compared to dry air - that's 1.5% thrust at N1. You may not consider 1.5% thrust significant, but those of us who worry about engine performance sure do.
And there nothing anecdotal about 37C and 90+% humidity if you're operating near the equator.