During early May 2026, hot
weather persisted over upper Thailand, with very hot weather in many areas of
the northern region and in some areas of the central and eastern regions. However,
during that period, a high-pressure system from China extended its ridge to cover
the northeastern region and the South China Sea. Meanwhile, upper Thailand remained
hot weather, coupled with the southerly and southeasterly winds prevailed over
upper Thailand, resulting in thunderstorms and gusty winds in many areas, with
hail reported in some places. In the middle of the month, rainfall increased in
both amounts and distribution across Thailand due to the influence of the
southwest monsoon prevailing over the Andaman Sea, Thailand and the Gulf of
Thailand. In addition, the low-pressure cell covered the Gulf of Martaban on
some days, and covering the lower northern and upper northeastern regions at
times. These conditions resulted in continuous rainfall across Thailand, marking
the onset of the 2026 rainy season on May 15. At the end of the month, the
southwest monsoon prevailing over Thailand was strengthened. In addition, the
monsoon trough lay across the northern, upper central, and lower northeastern
regions, extending into the low-pressure area covering the central coast of
Vietnam for few days. These conditions caused widespread rain across Thailand, with
heavy to very heavy rainfall at times. Flooding was reported in several areas with
flash flood and landslide occurred in some places. Monthly mean temperatures
were generally near to slightly above normal. Overall, the average rainfall across
Thailand this month was 21% higher than normal, with some stations setting new records
of the highest monthly total rainfall. The monthly rainfall exceeded normal
rainfall in almost all regions i.e. northern region 44.3 mm (26%), central region
5.3 mm (3%), southern region (east coast) region 32.9 mm (25%) and southern region
(west coast) 271.9 mm (90%). In contrast, rainfall was below normal rainfall in
the northeastern and eastern region by 5.4 mm (3%) and 34.0 mm (17%),
respectively. Further details are as follows:
Announcement Date 31 May 2026 15:52