Located entirely within a temperate zone, Uruguay has a climate that is relatively mild and fairly uniform nationwide. According to the Köppen Climate Classification, most of the country has a humid subtropical climate (Cfa). Only in some spots of the Atlantic Coast and at the summit of the highest hills of the Cuchilla Grande, the climate is oceanic (Cfb). Seasonal variations are pronounced, but extremes in temperature are rare. As would be expected with its abundance of water, high humidity and fog are common. The absence of mountains, which act as weather barriers, makes all locations vulnerable to high winds and rapid changes in weather as fronts or storms sweep across the country. Both summer and winter weather may vary from day to day with the passing of storm fronts, where a hot northerly wind may occasionally be followed by a cold wind (pampero) from the Argentine Pampas.