don't think it would make a huge difference if it was on a hill or not....in theory it would, but even then it would depend on the wind incidence angle to the hill, relative humidity, time of day, atmospheric pressure, dew point, atmospheric density, the partial pressure of water at the surface , planks constant, wet and dry bulb temperatures, scynoptic pressure patterns, the coriolis effect, localised micro climates , intergalacitc and solar radiation patterns, tidal flows, and the current geospatial positioning of the space time continueum... i recon less than a knot or two...