Nearly 20 houses in downtown Songkhla province in southern Thailand were damaged by a summer storm on Sunday, according to a local officer.

Most of the houses' roofs were blown away by gusty wind caused by the summer storm which continued in the area for at least an hour, a Tambon Administrative officer said.

Meanwhile, the Meteorological Department on Sunday issued a warning for people in 13 provinces to prepare for heavy downpour and possible flash floods.

Widespread scattered rain, heavy rains in some areas and flash floods were expected in northern provinces of Chiang Rai, Chiang Mai, Payao, Nan, Lumpang, Lumpoon, Uttraradit; central provinces of Phitsanulok, Phetchabun, Chantaburi, Trad; and southern provinces of Ranong and Phangnga.

There will also be strong wind-generated 2- to 3-meter-high waves in the Andaman Sea and the Gulf of Thailand. All shipping operations should proceed with caution and small boats should keep ashore during May 27-29, the department said.