When the atmosphere has been known to exceed this setting. There has to be a reason or logic behind this right? 7-2-4. High Barometric Pressure a. Cold, dry air masses may produce barometric pressures in excess of 31.00 inches of Mercury, and many altimeters do not have an accurate means of being adjusted for settings of these levels. When the altimeter cannot be set to the higher pressure setting, the aircraft actual altitude will be higher than the altimeter indicates.