The department is forecasting thunderstorms, lightning, and strong winds in most regions of the country, and even hail in some locations.
The dangerous weather will last at least until Monday in many regions, the department said.
It has warned residents to remain indoors during thunderstorms, and if they must venture outside, to avoid proximity to tall trees, billboards or flimsy structures.
People are also advised to refrain from using their mobile phones or wearing accessories made of metal during thunderstorms to reduce the chance of being struck by lightning.
Farmers have also been urged to take precautions to prevent storms from destroying their crops.
Small boats should remain docked on Sunday and Monday in the South, particularly in the Gulf of Thailand, which will see heavy rainfall and threatening waves.
The provinces (by region) forecast to be most affected by severe weather until Monday are:
North:
Chiang Mai
Chiang Rai
Kamphaeng Phet
Lamphun
Lampang
Nan
Phetchabun
Phichit
Phitsanulok
Phrae
Tak
Northeast:
Bueng Kan
Buriram
Kalasin
Khon Kaen
Maha Sarakham
Mukdahan
Nakhon Phanom
Nakhon Ratchasima
Nong Bua Lamphu
Nong Khai
Loei
Roi Et
Sakhon Nakhon
Sisaket
Surin
Ubon Ratchathani
Udon Thani
Central:
Ang Thong
Bangkok and vicinity
Chai Nat
Kanchanaburi
Lop Buri
Nakhon Pathom
Nakhon Sawan
Phra Nakhon Si Ayutthaya
Ratchaburi
Samut Songkhram
Samut Sakhon
Saraburi
Sing Buri
Suphan Buri
Uthai Thani
East:
Chachoengsao
Chanthaburi
Chonburi
Nakhon Nayok
Prachinburi
Rayong
Sa Kaeo
Trat
South:
Phetchaburi
Prachuap Khiri Khan
Weather information is available around the clock on the Meteorological Department's website or by calling 0-2399-4012-13 or 1182.