How does temperature at the top of a mountain differ from the temperature at sea level?

                   The Standard Atmosphere (SA) on which all instruments are calibrated for, says that the average adiabatic lapse rate (how cold it is with altitude) is 0.65 C per 100 meters.
But it can vary a lot. At the end of a night, during a high pressure with clear sky and little or no wind, it may be much warmer on the top of the mountain than down in the valley. This is because, in those conditions at night, the cold air being denser, sinks in the valleys and that even causes a wind called, a katabatic wind.
However, during daytime, the heat of the sun makes the air to rise again and if, on the average, it is colder with altitude, it is because the convection (rising air) is much much faster than the subsidence (sinking air):