The pressure ports are on the bottom of the unit. If the bottom is reasonably in the clear and horizontal, then it reads static pressure and wind should not affect it significantly. If the unit is tilted so that the ports sees dynamic pressure due to wind, then the altitude reading can be affected. Even with it horizontal, if there is some obstruction that traps the wind under the unit, it can cause elevations errors. Air blowing into the ports will cause an error toward lower elevation.