Its not just your region temps but your room temps. I live in Phoenix Arizona with similar temps as your city except for that it is very dry here. The point is that I use my room temps for ambient because I use AC to cool my room. Even if you don't have AC there is the differences between shade temps and direct sun temps. Now your regions humidity does affect the airs efficiency at dissipating heat.
http://physics.stackexchange.com/questions/45349/how-air-humidity-affects-how-much-time-is-needed-for-heating-the-air
So your regions humidity level (unless you have a dehumidifier or evaporative cooler) will affect your systems ability to react to temperature changes and the capacity of your air to retain heat but because it takes almost no time to cool a CPU and GPU down after the load is removed, this affect is almost null.
So what is your room temperature? Do you have an AC unit or a Evaporative Cooler that can lower your room temps?