Nepal’s air quality, which remained toxic for the past several weeks, has improved significantly in recent days, thanks to pre-monsoon activities. Rainfall and winds now provide much-needed relief from hazardous conditions.

On Sunday afternoon, Kathmandu Valley witnessed brief rainfall and strong winds, which helped reduce air pollution levels.

According to IQAir, a Swiss group that collects air-quality data from around the world, the air quality in most places of the Valley was moderate—PM2.5 levels below 100 micrograms per cubic metre.

PM2.5 refers to particulate matter (solid or liquid droplets) in the air less than 2.5 micrometres in diameter. These are the most dangerous pollutants that can get past the nose and throat to penetrate the lungs and even the bloodstream. PM2.5 particles are small and tend to remain suspended in the air for extended periods, increasing the risk of inhalation.

Until a few days ago, air quality in most places of the Valley had reached very unhealthy and hazardous levels. Hospitals in the Valley had reported a sharp rise in respiratory cases, and the general public also complained about a burning sensation and redness in the eyes.

The air quality in Kathmandu Valley began to deteriorate in the last week of January. Of late, haze mixed with polluted air has blanketed the entire country, directly affecting the general public.

Experts point to the authorities’ apathy for enforcing measures to improve air quality as a key factor in the worsening pollution levels. Poor air quality has not only affected people’s health, but also hit the economy and hindered overall development, according to experts. Polluted air has long been taking a huge toll on public health in Nepal.

However, with the start of pre-monsoon activities last week, air quality has improved significantly.

The Meteorological Forecasting Division of the Department of Hydrology and Meteorology recorded 169 mm rainfall in Jhapa in the 24 hours until Friday morning, which the division termed “very heavy”. The division recorded 126 mm of rainfall in Chitwan and 102 mm in Lamjung, both of which fall in the “very heavy” category. Udayapur recorded 98 mm of rainfall, and Gorkha recorded 91 mm, which the division said is “heavy”.

The division classifies moderate rainfall as 10 to 50 mm, heavy as 50 to 100 mm, very heavy as 100 to 200 mm, and extremely heavy as 200 to 300 mm, according to the met officials.

“The rain and other premonsoon activities have brought much-needed relief to the public,” said Barun Paudel, a senior meteorologist at the division. “Westerly low-pressure systems and local systems are responsible for increased premonsoon activity, rainfall, winds, hail, and thunderstorms. Premonsoon rainfall also brings relief to farmers.”

Meteorologists say that premonsoon activities are a normal phenomenon, which will also occur in the coming days. They say the weather will not be disturbed all day. “After rain, wind and other weather events, the weather will be cleared again,” said Paudel.

Met experts ask the general public to be cautious about the changing weather and take precautions. They said that one could get hurt from the falling trees, branches, and signboards due to strong winds. Likewise, the risk of hail and thunderstorms will increase during the premonsoon season.

The Met Office predicted generally cloudy conditions over hilly and mountainous regions, including Koshi, Karnali, and Sudurpaschim Province, on Sunday night. There is also a possibility of moderate rain and snowfall, with thunder and lightning, at a few places in the country's mountainous region.

Moderate rain with thunder and lightning is likely at a few places in the hilly regions of Koshi, Lumbini, Karnali, and Sudurpashchim provinces and at a few places in the hilly regions of Bagmati and Gandaki. There is also the possibility of moderate rain with thunder and lightning at one or two places in the Tarai regions of Lumbini and Sudurpashchim provinces.