also, the wet seasons are spring and autumn, but the spring one is earlier (March), and autumn is the wetter season. Even during the wet seasons, rain is irregular and unreliable. Winters in these regions are cold, with strong winds and high humidity, despite the low precipitation. Except for mountain areas, the northern foothills of the Sistema Iberico are the coldest area, and frost is common. Summers are hot and cloudless, producing average daytime temperatures that reach the mid- or upper 30s °C (low 90s to low 100s °F) in the northern Meseta and the upper 30s °C (upper 90s to low 100s °F) in the southern Meseta; nighttime temperatures, however, drop to the upper teens °C (low to mid 60s °F). The Ebro Basin, at a lower altitude, is extremely hot during the summer, and temperatures can exceed . Summer humidities are low in the Meseta Central and in the Ebro Basin, except right along the shores of in the Rio Ebro, where humidity is high. A maritime climate prevails in the northern part of the country, from the Pyrenees to the northwest region, characterized by relatively mild winters, warm but not hot summers, and generally abundant rainfall spread out over the year. Temperatures vary only slightly, both on a diurnal and a seasonal basis. The moderating effects of the sea, however, abate in the inland areas, where temperatures are more extreme than temperatures on the coast. Distance from the Atlantic Ocean also affects precipitation, and there is less rainfall in the east than in the west. Autumn (October through December) is the wettest season, while July is the driest month. The high humidity and the prevailing off-shore winds make fog and mist common along the northwest coast; this phenomenon is less frequent a short distance inland, however, because the mountains form a barrier keeping out the sea moisture. The Mediterranean climatic region extends from the Andalusian Plain along the southern and eastern coasts up to the Pyrenees, on the seaward side of the mountain ranges that parallel the coast. Total rainfall in this region is lower than in the rest of Spain, and it is concentrated in the late autumn–winter period. Generally, rainfall is slight, often insufficient, irregular, and unreliable. Temperatures in the Mediterranean region usually are more moderate in both summer and winter, and diurnal temperature changes are more limited than those of the continental region. Temperatures