Source: The Library Of Congress Country Studies
Peninsular Spain experiences three climatic types: continental, maritime, and Mediterranean. The locally generated continental climate covers the majority of peninsular Spain, influencing the Meseta Central, the adjoining mountains to the east and the south, and the Ebro Basin. A continental climate is characterized by wide diurnal and seasonal variations in temperature and by low, irregular rainfall with high rates of evaporation that leave the land arid. Annual rainfall generally is thirty to sixty-four centimeters; most of the Meseta region receives about fifty centimeters. The northern Meseta, the Sistema Central, and the Ebro Basin have two rainy seasons, one in spring (April-June) and the other in autumn (OctoberNovember ), with late spring being the wettest time of the year. In the southern Meseta, 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. Continental winters 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 warm and cloudless, producing average daytime temperatures that reach 21° C in the northern Meseta and 24 to 27° C in the southern Meseta; nighttime temperatures range from 7 to 10 C. The Ebro Basin, at a lower altitude, is extremely hot during the summer, and temperatures can exceed 43 C. 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 9 to 18 C 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 higher in both summer and winter, and diurnal temperature changes are more limited than those of the continental region. Temperatures in January normally average 10 to 13 C in most of the Mediterranean region, and they are 9 C colder in the northeastern coastal area near Barcelona. In winter, temperatures inland in the Andalusian Plain are slightly lower than those on the coasts. Temperatures in July and August average 22 to 27 C on the coast and 29 to 31 C farther inland, with low humidity. The Mediterranean region is marked by Leveche winds--hot, dry, easterly or southeasterly air currents that originate over North Africa. These winds, which sometimes carry fine dust, are most common in spring. A cooler easterly wind, the Levante, funnels between the Sistema Penibetico and the Atlas Mountains of North Africa.
Data as of 1988