Another point to remember is not to store your batteries in a hot location ie your parked car.....hope that isn't too obvious. ?
The temp of the batteries is the air temp plus heating due to being in direct sunlight (the road surface can be hotter than the air temp because it absorbs the sunlight and converts it into thermal energy) plus heating due to the battery discharging (flying in sport mode heats the battery faster) minus cooling due to air flow (the fan inside). And yes, high attitude has lower density air so the fan is less effective. At 90°F air temp and in full sun, you should start being concerned about battery overheating.
If the battery overheats and you ignore warning messages, the drone may land on it's own. In addition, overheating the battery will shorten its life.
Warm air is less dense than cooler air, but battery issues will be a bigger problem than the reduced lift provided by the warmer air.
There are a host of folks on this forum that worry about keeping their batteries warm enough by the way....?
Enjoy your drone!