Hills do make a big difference. We are part way down a hill... neighbours further up the hill behind us don't get frosts but as you go down the driveway you can feel a noticeable drop in temperature. We get the occasional light frost here when the temp gets down to -2C or -3C but a further 100m down the bottom of the driveway on the flats has a frost most winter mornings... everything is totally white and the temp is much cooler. There would be at least 5 degrees difference between the neighbours behind us and the flats at the bottom.