The Meteorological Forecasting Division has said that a westerly wind system, which is all set to enter the country from Sudurpaschim Province, will result in rainfall across the country on Sunday.

Several districts of the hill and mountainous regions of Bagmati Province, including the Kathmandu Valley, Gandaki, Karnali and Sudurpaschim provinces, witnessed heavy rainfall accompanied by thunderstorms on Saturday.

The Kathmandu Valley on Saturday recorded 31.5 mm rainfall, the highest in the country. The downpour caused waterlogging in various areas including Sundhara and Tripureshwar, among others, which affected traffic as well as pedestrians. Meanwhile, Pokhara recorded 23.2 mm rainfall, Taplejung 22.9 mm and Lumle 19.6 mm.

“The weather system is moving towards the eastern part of the country, so the rainfall along with the thunderstorms will continue on Saturday night as well,” said Govinda Kumar Jha, a meteorologist at the division, which is under the Department of Hydrology and Meteorology.

The met office said all regions, including the Tarai districts, will witness rainfall on Sunday. The office has advised people to remain alert to avoid any untoward incidents from lightning and strong winds.

The pre-monsoon rainfall has helped in lessening the temperature of the Tarai region, which had crossed 40 degrees Celsius about two weeks ago.

The maximum temperature had risen by 3 degrees Celsius in most parts of the country, higher than the average for this time of the year in previous years.

The mercury had soared to more than 40 degrees Celsius in many districts of the Tarai region, including Kapilvastu, Rupandehi, Parsa, Bara, Sarlahi, Dhanusha, Saptari and Siraha. Hot air started blowing around 10 am, disrupting daily life.

The met office had forecast mild to moderate heat waves in some districts and extreme heat waves in other places. Lack of rainfall for a long time triggered incidents of forest fires across the country which led to a general deterioration in the air quality. Smoke and haze covered the Kathmandu Valley and a few other places, affecting many domestic flights.

AQ AirVisual, a Swiss group that collects air-quality data from around the world, had ranked Kathmandu as the most polluted city in the world earlier this month.

On Saturday, at 6:45 am, the Kathmandu Valley’s air quality index reached 189. According to the United States Environment Protection Agency’s air quality index, when air pollutant PM2.5 reaches 151 to 200 μg/m3, the air quality is considered unhealthy; everyone may experience problems, with sensitive groups experiencing more severe effects. But in the afternoon, it declined to 124.

The rainfall that started on Saturday was credited to the western disturbances and the locally-formed weather system, which develops during the pre-monsoon season. The rainfall is expected to help in further lessening the incidents of forest fires.