In 2011, several severe natural disasters had taken place in Thailand, particularly since March onwards. The typical weather in March when the hot season is dominant throughout the country had generally been hot and humid with scarce rainfalls. But in March 2011, a cold snap together with occasional rainfalls occurred in upper Thailand almost the whole month. High-pressure areas extending their ridges from China to cover upper Thailand periodically were found to be the causes of such phenomenon.
Also in March 2011, an active low pressure cell covered the middle part of the Southern Region and caused intense rainfalls almost the whole period. Incessantly heavy and very heavy rainfalls observed in many areas caused unprecedentedly severe flash floods over huge areas of the majority of the southern provinces : Chumphon, Surat Thani,
Nakhon Si Thammarat, Songkhla, Patthalung, Narathiwat, Yala, Trang, Phang Nga, Krabi, and Satun. In addition, both landslides and mudslides were also reported in Chumphon,
Surat Thani, Trang, and Krabi. The total amount of monthly rainfalls countrywide last March was the highest one for the last 36 years (1974 - 2010). Besides, new highest amounts of 24 hours rainfalls as well as new lowest minimum daily temperatures were recorded in several areas during such period too. Consequently, these situations were considered very unusual, compared to what had normally occurred.