The thermal low-pressure cell covering the North and Northeast would raise the temperature during daytime, while the southerly and southwesterly winds would bring isolated thundershowers and gusty winds to some areas in upper Thailand, the department said.
It advised people in affected areas to stay indoors and stay away from large trees and unsecured billboards. Drivers should exercise caution when out on the roads during thundershowers, and farmers should prepare for damage to their crops and livestock, the department added.
Meanwhile, the east and west coasts of the South would experience isolated thundershowers on Friday due to the influence of the southeasterly winds prevailing over the Gulf and the Andaman Sea, the department said.
The weather forecast for the next 24 hours is as follows:
Bangkok Metropolitan area: Hot to very hot day with isolated thundershowers in 10 per cent of the area. Minimum temperature of 28-30 degrees Celsius and highs of 37-42°C.
North: Hot to very hot day with isolated thundershowers and gusty winds mostly in Mae Hong Son, Chiang Mai, Chiang Rai, Phayao, Nan, Tak and Phetchabun provinces. Lows of 23-29°C and highs of 38-43°C.
Northeast: Hot to very hot day with isolated thundershowers and gusty winds, mostly in Loei, Nakhon Ratchasima, Buri Ram, Surin, Si Sa Ket and Ubon Ratchathani provinces. Lows of 25-29°C and highs of 42-44°C.
Central: Hot to very hot day with isolated thundershowers and gusty winds, mostly in Uthai Thani, Kanchanaburi, Suphanburi and Ratchaburi provinces. Lows of 26-29°C and highs of 38-43°C.
East: A hot day with isolated thundershowers and gusty winds, mostly in Nakhon Nayok, Chonburi, Rayong, Chanthaburi and Trat provinces. Lows of 26-29°C and highs of 35-42°C. Waves less than a metre high and over a metre high during thundershowers.
South (east coast): Hot day with isolated thundershowers mostly in Surat Thani, Nakhon Si Thammarat, Songkhla, Pattani, Yala and Narathiwat provinces. Lows of 24-28°C and highs of 35-40°C. Waves less than a metre high and over a metre in thundershowers.
South (west coast): Hot day with isolated thundershowers mostly in Ranong, Phang Nga, Krabi, Trang and Satun provinces. Lows of 26-28°C and highs of 36-38°C. Waves less than a metre high and over a metre in thundershowers.