Not strange at all. AFR and HP will vary with pressure, temperature and humidity. I understand the relationship and mentally adjust accordingly.
The safest way to tune is for high pressure, cold ambient temps, & low humidity. If the tuning is spot on in that scenario then it will automatically become relatively richer in warm & humid weather, all other things equal.
I have to chuckle when some say "turn the pilot screws richer in warm weather", because, all other things equal, the mixture automatically becomes richer in warm weather.
