There's no possibility to manipulate temperature yourself at the environment settings unless you select a Precipitation but what if you want something different.
The temperatures are pre-set depending on the season you have selected. There is no option to manually input your own temperature.
Since that is the way they designed it - I would guess that is the way it is meant to be. Since one does not need to worry about things like density altitude and a temperature range of 20 or so degrees to be season appropriate - what would setting the temperature accomplish in the simulation?