The Alps serve as a watershed for Europe's three major kinds of weather systems that influence Austrian weather. The Atlantic maritime climate from the northwest is characterized by lowpressure fronts, mild air from the Gulf Stream, and precipitation. It has the greatest influence on the northern slopes of the Alps, the Northern Alpine Foreland, and the Danube Valley. The continental climate is characterized by low-pressure fronts with precipitation in summer and high-pressure systems with cold and dry air in winter. It affects mainly eastern Austria. Mediterranean high-pressure systems from the south are characterized by few clouds and warm air, and they influence the weather of the southern slopes of the Alps and that of the Southeastern Alpine Foreland, making them the most temperate part of Austria. One peculiarity of the Mediterranean weather systems is the föhn, a warm air mass that originates in the African Sahara and moves north rapidly, periodically raising temperatures up to 10° C in a short period of time. Many people respond to this rapid weather change with headaches, irritability, and circulatory problems. During the winter, the rapid warming that accompanies a föhn can thaw the snow cover in the Alps to such an extent that avalanches occur. Given the importance of Alpine skiing for the Austrian tourist industry, December is the month during which the weather is watched with the greatest anticipation. As a rule, Atlantic maritime weather systems bring snow, and continental weather systems help keep it. However, a predominance of cold, dry continental systems or warm Mediterranean ones inevitably postpone the beginning of the ski season. In the summer, Mediterranean high-pressure systems bring warm, sunny weather. Data as of December 1993
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