The climate of the Tibetan Plateau is highly affected by its terrain. The numerous high mountain ranges act either as barriers to keep out southern tropical and equatorial air or as barriers keeping in the arctic air from the north. There is much variation, but generally it is very dry, with low humidity, strong winds, and a large fluctuation in seasonal temperatures. There is often a strong heating of the land in summer months, and a sharp chilling in winter. In the wintertime, the plateau usually experiences cold but calm weather, with little snow except in the higher mountain ranges. In most other areas, snow quickly evaporates due to dryness. Nearly all of the regions yearly rainfall occurs in the heat of summer, and generally falls all at once and in specific areas. These monsoon rains occur more in the lower regions in the east and south. Daytime temperatures vary for different regions, ranging from 25-30°C in summer to -9 to -35°C in winter. The temperatures at night can drop dramatically even in summertime. In some areas, it may be 30°C in the daytime and drop to -15°C at night. In many areas there may be sudden strong winds, causing severe dust storms due to the aridity of the region. In general, when traveling in this region, it is good to have several layers of clothing that one can put on or remove as the day progresses, in order to stay comfortable both in the heat of summer days, and the chill of the nights. One should remember that this is a very large area we are talking about and so temperatures will vary widely depending on the specific region you will be traveling to, but a vague, general temperature range by western standards would be as follows: