The department said that a strong low-pressure mass in the Andaman Sea would influence the southwest monsoon to become stronger, which would unleash heavy rains in the North, Central and South during the period.
The department said the 11 northern provinces that could be hit by floods during the period are: Mae Hong Son, Chiang Mai, Lamphun, Lampang, Phrae, Nan, Uttardit, Tak, Sukhothai, Phitsanulok and Phetchabun.
It also warned residents of Chonburi, Rayong, Chanthaburi and Trat to watch out for heavy rains.
The department said the southern provinces that could be hit by heavy rains and floods during the period were: Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung, Songkhla, Ranong, Phang Nga, Phuket, Krabi, Trang and Satun.
The department said it had coordinated with the 26 provincial administrations to monitor the weather conditions and prepare emergency teams to help affected people as soon as possible.