I think the rule of thumb is that every 100 meters lowers the temperature by 1C. So if you know that on the ground the temperature is 10C and you know the mount

I think the rule of thumb is that every 100 meters lowers the temperature by 1C. So if you know that on the ground the temperature is 10C and you know the mountain is 600 meters then on top of that mountain the temperature would be around 4C. But maybe this rule of thumb doesn't apply everywhere and everytime.