Thailand is transitioning from winter to summer - with rain expected in Bangkok over the next week.

The weather forecast on Sunday predicted a significant chance of rain in Greater Bangkok from Tuesday to Saturday.

Up to 40% of the Bangkok metropolitan area will see rain over the five-day period, with possible downpours between Thursday and Saturday, the Meteorological Department said.

Despite the wet weather, temperatures are expected to climb to 37°C, with a low of 24°C. Temperatures were between the late 20s and early 30s for the week ending Sunday.

The exact start of the summer season, which normally arrives in late February or early March, is determined by a change in direction of the prevailing winds.

Last year, summer officially began on March 3, according to the department.

Meanwhile, pollution levels around the city are going down, with most measured locations for the Air Quality Index dropping below last week's danger zone. 

These are readings as of late Sunday night:

The level of dust particles in the city should further decrease and are expected to stay at the safety standard in all areas of the city today, said permanent secretary of the Natural Resources and Environment Ministry Wijaran Simachaya.

The airborne particulate matter surged above the safety limit of 50 µcg in many areas of Bangkok last week, a level that can endanger people's health.

Its size of less than 2.5 micrometres in diameter means it can enter the lungs easily if people do not wear masks.

Mr Wijarn said cloud-seeding to make artificial rain to bring down dust levels in Bangkok's five surrounding provinces cannot yet start due to unsuitable weather conditions.