Expect ambient temperatures to DIRECTLY effect system temperature, a 5 degree rise in ambient should equate to a 5 degree rise in system temp.
The cooler can only bring the system as cool as the ambient air, for the ambient air is what's being used to dissipate the heat from the heatsink.
Also take into mind that the air is cooler near the ground, if you have your PC lower to the ground, this may also effect temperature.
In the winter, by opening and closing my windows during gaming I am capable of effecting how much I can overclock my GPU due to the temperature difference, this also applies to the summer with AC on/off.
I live in Las Vegas NV, where it can get quite hot, and while the AC in our home does its job, my room tends to get the hottest at a peak of about 85 ambient room temp!
85 doesn't sound too terrible, my room often hits above 100F due to poor room circulation.... That and I own a GTX 480. But seriously it's a sauna here in the summer.