🇹🇭Thailand

Thailand (approximately 513,000 km²) occupies the heart of mainland Southeast Asia between 5°–21°N, bordered by the Andaman Sea (937 km coastline) to the southwest and the Gulf of Thailand (1,875 km coastline) to the southeast, encompassing diverse tropical climate zones from monsoonal rainforests to savanna.

The kingdom spans varied topography: the mountainous northern region, where Doi Inthanon reaches 2,565 m, with temperate upland valleys; the vast northeastern Khorat Plateau covering one-third of the country and prone to drought; the fertile Chao Phraya River basin descending through the low-lying Central Plains; and the narrow southern peninsula with year-round tropical humidity.

The climate is predominantly Köppen Aw (tropical savanna) and Am (tropical monsoon) with mean annual temperatures ranging from the mid-20s °C in the north to about 28°C in the southern peninsula. Annual precipitation varies dramatically from under 1,200 mm on the leeward sides of the central valleys to over 4,000 mm on windward coasts such as Ranong.

Bangkok (Chao Phraya delta, 2 m) has highs of 33°C in January (nights 23°C) and about 34°C in July (nights 26°C), 1,500 mm precipitation May–October. Chiang Mai (304 m) records highs of 30°C in January (nights 16°C) and 32°C in July (nights 24°C), 1,150 mm with dry-season smoke episodes from agricultural burning. Udon Thani in the northeast receives about 1,400 mm a year.

Major impacts include the December 2004 Indian Ocean tsunami, killing about 5,400 people including many foreign tourists, with the worst toll at Khao Lak; the July 2011–January 2012 Great Floods inundating 65 of 77 provinces, killing 815, and causing $46.5 billion in damages; and the April 2024 Southeast Asian heatwave reaching 44.2°C in Lampang. Rising sea level and subsidence (10–30 mm/year in the early 2000s) affect Bangkok's long-term stability.

Our archive covers 53 Thai cities with daily ERA5 reanalysis data going back to 1940. The hottest July afternoons are in Nakhon Ratchasima, with average highs around 33.2°C, while Chiang Mai has the coldest January nights, with average lows near 15.1°C. Comparing the last decade against the 1940–1970 baseline, mean temperatures across these cities have risen by about 1.4°C.