Thailand is about the same size as France and has a coastline on the Gulf of Siam which is part of the Pacific Ocean. The country has an equatorial climate in the extreme south while the centre and north have a tropical monsoon climate.
Much of Thailand has abundant rather than excessive rainfall, and this is largely confined to the months from May to October. During this season the weather is dominated by the south-west monsoon blowing from the Indian Ocean, bringing warm, humid air and much cloud. November to April are much drier with rain falling only on a few days a month. This is the period of the north-east monsoon when the wind is blowing overland from China or Indo-China and the air is consequently much drier.
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 north-east monsoon is definitely cooler. In most of Thailand the hottest months are April and May before the cloudier, rainy weather brought by the south-west monsoon. Sunshine amounts everywhere are 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.