Sceptre,
Technically, no you don't and any other terrain mod that you use will show up in Autumn, Winter and Summer... BUT. There are several textures in the mod package that will show up as desert at any time of the year regardless of when you fly such as the surrounds for the FARP landing pads, the Bunker fortifications and Command Post structures.
You'll also note that with the newer complete package that I have posted, all of the Stock DCS vehicles and Beczl's vehicle pack will show up in any season with desert camo on. This is another limitation of the way that textures are implemented in the current DCS engine.
My suggestion is, if you want to fly in the desert, activate this mod before you start DCS, if you don't, disable it before you start DCS. That way you can have the best of both worlds and you don't need to remove any other terrain mods installed previously (just say yes when JSGME warns you that it will change files already used by mod XYZ).
I hope that clears up your question.
Highway.