Temperatures in the region are forecast at 24-26°C minimum and 34-35°C maximum.
Heavy rain forecast for Central, Eastern and Southern regions
The Central region is forecast to see scattered thundershowers and isolated heavy rain in Nakhon Sawan, Uthai Thani, Chai Nat, Lopburi, Saraburi, Kanchanaburi, Ratchaburi, Nakhon Pathom and Samut Sakhon.
Temperatures in the Central region are expected to range from 24-27°C to 33-38°C.
In the East, scattered thundershowers and isolated heavy rain are forecast in Nakhon Nayok, Prachinburi, Sa Kaeo, Rayong, Chanthaburi and Trat, with temperatures ranging from 24-28°C to 31-35°C.
The southern east coast will see scattered thundershowers, mainly in Prachuap Khiri Khan, Chumphon, Surat Thani, Nakhon Si Thammarat, Phatthalung and Songkhla.
On the southern west coast, fairly widespread thundershowers and isolated heavy rain are expected in Ranong, Phang Nga, Phuket, Krabi, Trang and Satun.
Ships urged to avoid thundershowers
The TMD said waves in the upper Andaman Sea could reach about 2 metres, while waves in the lower Andaman Sea and the Gulf are forecast at 1-2 metres.
In thundershowers, waves could rise above 2 metres.
All ships in the Andaman Sea and the Gulf are advised to proceed with caution and avoid sailing through thundershowers.
Bangkok rain clouds moving northeast
For Bangkok and surrounding provinces, the department reported light to moderate rain over several districts and nearby areas.
Rain was detected in Bang Khun Thian, Chom Thong, Thung Khru, Bang Bon, Bang Khae, Nong Khaem, Phasi Charoen, Taling Chan, Bangkok Noi and Thawi Watthana.
Nearby provinces affected included Nonthaburi, Samut Prakan, Pathum Thani, Phra Nakhon Si Ayutthaya, Nakhon Pathom, Samut Sakhon, Samut Songkhram, Ratchaburi and Suphan Buri.
The rain clouds were moving northeast. Although the rain had begun to weaken, the department said they were still expanding into more parts of Bangkok.
Inner Bangkok also affected
Rain clouds were also moving across or towards Rat Burana, Bang Kho Laem, Khlong San, Sathon, Bang Rak, Samphanthawong, Phra Nakhon, Pom Prap Sattru Phai, Dusit, Bang Phlat, Pathum Wan, Phaya Thai, Ratchathewi, Yan Nawa, Khlong Toei, Watthana, Din Daeng, Bang Sue, Phra Khanong, Bang Na, Huai Khwang, Chatuchak and Lak Si.
The rain was also expected to affect Nonthaburi, Pathum Thani, Phra Nakhon Si Ayutthaya and Samut Prakan.
Between 5.30pm and 6pm, rain was expected to continue over Phaya Thai, Chatuchak, Lak Si, Khlong Toei, Ratchathewi, Din Daeng, Watthana, Huai Khwang, Phra Khanong, Bang Na, Don Mueang, Bang Khen, Lat Phrao, Wang Thonglang, Bang Kapi, Suan Luang and Prawet.
The department said rain clouds were expected to cover these areas for more than one hour.
Bangkok forecast: scattered storms and isolated heavy rain
For the Bangkok Metropolitan Region, the TMD forecast scattered thundershowers and isolated heavy rain from Wednesday evening to Thursday evening.
Temperatures are expected to range from 25-27°C to 34-36°C, with southwesterly winds of 10-25km/h.
