Thailand, in Southeast Asia, is about the same size as France. It is bordered by Myanmar on the north and west and by Laos and Cambodia on the east. It has a coastline on the Gulf of Thailand, which is part of the Pacific Ocean. The south of the country consists of the narrow Kra Isthmus dividing the Pacific from the Indian Ocean and joining the Malayan peninsula to the mainland of Southeast Asia. Situated between 6° and 20°N, the country has an equatorial climate in the extreme south while the centre and north have a tropical monsoon climate similar to that of Myanmar. The north is hilly and even mountainous with land rising over 2,000 m/7,000 ft, but most of the centre and east of Thailand is low-lying with only gentle hills and slopes.
Most of Thailand has abundant, but not excessive, rainfall and this is largely confined to the months May to October. During this season the weather is dominated by the southwest monsoon blowing from the Indian Ocean and bringing warm, humid air, and much cloud. The months November to April are much drier, with rain only falling on a few days a month. This is the period of the northeast monsoon when the wind is blowing overland from China or Indochina and the air is consequently much drier. In the Kra Isthmus these winds bring more rain since they are more likely to have their origin in the Pacific Ocean or to have blown across the Gulf of Thailand. More rain falls in the south at this time but the extreme north is virtually dry for two or three months.
In the centre and south of the country there is no great variation in temperature from month to month, but in the north the period of the northeast monsoon is definitely cooler. This may be seen by comparing the table for Chiang Mai in the northern hills with that for Bangkok in the south-centre of the country. In most of Thailand the hottest months are April and May, before the cloudier, rainy weather brought by the southwest monsoon. Sunshine amounts are everywhere lowest during the months June to September, when they average four to five hours a day. During the rest of the year they average nine to ten hours.
The weather of the wet season is oppressive over most of Thailand because of the combination of high temperature and humidity. During the sunnier months of the dry season conditions are fresher and there is usually more wind. Although severe heat stress is rare in Thailand, visitors will find the weather of the wet season rather uncomfortable.
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