Thailand is located in a tropical climate zone. In the tropical zone of Asia, there is a change in air currents: in winter, the trade wind dominates, in summer – the monsoon, which determines the seasons of the year. Characteristic features of the climatic regime of Thailand are due to the presence of mountains in the north, which protect its territory from the influence of the winter trade wind, so the cool season is poorly expressed.
In the northern, northeastern and central regions of Thailand, there are 3 seasons depending on the amount of precipitation, in the southern regions – 2. In the east of the country a special climate has formed with a fairly even distribution of precipitation during most of the year and with a sharp increase in September. .
During the influence of the trade wind (from November to February), mild weather sets in throughout the country. The average temperature in December, the coldest month, in the north is +19 degrees, in the south – +26. At the same time, in the daytime, the air in these areas warms up to +27 and +30, respectively. In winter, nighttime temperatures in most of Thailand do not fall below +20; only the mountainous areas in the north are characterized by lower temperatures – in January they are +10: +12 degrees, and on some days the thermometer can drop to 0.
The period from December to February in most parts of Thailand is the dry season. At this time, cloudy weather prevails with light rain; average monthly rainfall does not exceed 40 – 50 mm. In the south, the driest month is February; in December and January, the amount of precipitation varies depending on location from 30 mm in the northernmost regions to 370 mm in the southernmost.
From March to May in the northern, northeastern and central regions of the country lasts summer. The sun is already hot in the morning, and by noon the temperature reaches +32: +35 degrees. At night, the air is cooled to +25. In April, precipitation becomes more intense, and in May the third season begins in these areas – the monsoon rainy season, which lasts until the end of October. Thunderstorms occur almost daily, but they quickly end, and after them the sun shines brightly again. During this period, daytime temperatures drop by 2 to 3 degrees.
The maximum amount of precipitation falls in September-October and is 230 – 250 mm.
In the south, the rainy season begins in March and lasts until January, with the maximum precipitation in different areas occurring at different times. In September-October, Phuket floods, in November-December – Koh Samui (more than 300 mm of precipitation falls in a month) – At the same time, in the remaining months of the rainy season the amount of precipitation exceeds 100 mm. The more south the territory is located, the less the dry season lasts. The hottest month is August, when during the daytime the air warms up to +32 … 34, and at night it cools to +25.
The central plain, the North and the Northeast receive an average of 1000–1100 mm of precipitation per year, of which more than 90% fall in the wet season, which lasts from May to October. In the South and Southeast, the average annual rainfall is 2300–2500 mm, and their number does not change significantly from month to month.
The dry season is especially noticeable in the Northeast. On the fields, the withered soil is petrified and cracks. Due to the lowering of the groundwater level, ponds, shallow lakes, marshes and ditches dry up. Some rivers become shallow and become unsuitable for navigation, and sometimes lose flow.
Monsoon rains begin in April-May, and in early June the earth is so wetted that it can be processed and sown. In July, irrigation canals are filled with water following the rivers, which are widely flooded on the Central Plain. As a result of land in the delta. Chaphraya flooded almost entirely. To protect against water, local people build houses on stilts. In recent years, due to extensive deforestation, the adverse effect of seasonal floods and droughts has intensified.