Hi Yoshi and welcome to the forum. I live in the "mountains" and have now experienced three winters here. Having read your first post and the subsequent replies, you will no doubt still be a bit muddled.
Are you thinking about a new build or pre-built?
Moving to higher ground automatically means it will be cooler than the coast. The heat in the Fethiye area can become quite oppressive, especially in July and August. In these months, it is usually 4-6 degrees cooler up here and you will be grateful for that. The downside is of course is the temperature difference is still there at other times. But hey... you can't have everything and no matter where you choose to live, it is never going to perfect. There are always compromises to be made unless you are rich enough to have a place in Fethiye/Calis in the winter and a place in Uzumlu in the summer!
As regards the actual temperatures up here, I can give you some figures. Where we live, the maximum last year was a day in August when it reached 36.7. Average temp during the summer months is around 28 - 32. We do not have air conditioning, as there is always a mountain breeze to cool you off. In winter, the temp is usually between 10 and 14. But this part of Turkey usually gets a cold snap for at least a couple of days with northerly winds. Then the temp can go minus, but we love those clear frosty mornings.
There is still a lot of sun in winter (probably more than the UK in summer) and it is still powerful so it can feel very pleasant. It is also less humid here than near the coast (for obvious reasons).
But that's the thing- we do not have weather, we have climate! The seasons are well defined and the change from one to another can happen in days. Winter season is usually quite short lived. This year it did last longer than the year before from around December to mid April, when we stopped lighting the fire of an evening.
Hope this helps.