The Northern Regional Hydro-Meteorological Centre said the heatwave would persist from July 15 to July 17, with daytime highs of 35-37 degrees Celcius and minimum relative humidity of 55-60 per cent.
The hot weather is being driven by a weak low-pressure trough stretching across the northern plains and the north-central region, the centre said.
Forecasters issued a Level 1 natural disaster warning for the heatwave.
They said prolonged high temperatures and low humidity could increase the risk of fires in residential areas because of higher electricity demand, as well as forest fires.
Health officials also warned that prolonged exposure to the heat could lead to dehydration, exhaustion and heatstroke, particularly for people working or spending long periods outdoors.
The weather agency noted that actual temperatures outdoors could be 2-4 degrees Celcius higher than official readings, especially in built-up areas where concrete and asphalt absorb and retain heat.
