The threat of toxic smog has receded temporarily in Lahore on Thursday due to overnight rain in certain regions.

According to Met department sources, the current spell of rain is expected to continue till Friday with wind direction to change within next 24 hours.

Currently, strong winds coupled with rain, from east and southeast direction, have blown away pollutants from the provincial capital. However, this is only a temporary relief for the citizens as the fifth season of toxic smog will continue to engulf horizon from November till February.

On Thursday, widespread rain/thunderstorm (with heavy falls at a few places) is expected in districts of upper Punjab, Kashmir, Gilgit Baltistan and Islamabad, at scattered places in districts of Khyber Pakhtunkhwa and central Punjab.

Snowfall over high mountains and hailstorm in plain areas are also expected during the period.

Concerns around poor air quality are mounting for the last four years as the smog has deprived the people of sunshine and dusk-hour charm, and unfolded severe health risks with respiratory diseases, particularly for the children and the elderly.

Officials and several politicians have claimed that stubble burning in Indian Punjab, and the sudden change of direction of wind last night was responsible for thick layers of smog in Lahore.

After a sudden spike in Lahore’s Air Quality Index (AQI), which measures the concentration of poisonous particles, from less than 200 to more than 500, the chief minister announced closure of public and private schools on Thursday. This is the first time that smog has forced closure of schools.

The city’s air quality index (AQI), which measures the concentration of poisonous particles, was recorded at 216 in the "poor" category on Wednesday.

At the weekend, New Delhi experienced its worst air quality day since 2016 with an AQI of 494, in the "severe" category — 500 is the maximum score and anything above 400 is considered hazardous to health.

Just before midnight, Chief Minister Usman Buzdar tweeted: “Due to sudden increase in smog, all schools in Lahore will remain closed tomorrow. We are closely monitoring the #LahoreSmog situation. Administration is already on high alert and have tasked them to escalate actions against crop burning and other factors that contribute to smog.”

As per Lahore US consulate Air Quality Monitor feed, the level of smog was hazardous and at 10pm, Lahore’s AQI was PM2.5 - 580.

The itching air, complicating respiratory systems of the people, was alarming by the evening. And for that reason, #LahoreSmog was the top trend on Twitter.

A group of students have petitioned the Lahore High Court seeking change in the AQI measurement system, and implementation of the Smog Policy.

Smog which occurs mainly because of intense air pollution can also be defined as a mixture of various gases with dust and water vapor. Smog also refers to hazy air that makes breathing difficult.

Smog can be responsible for any ailment from minor pains to deadly pulmonary diseases such as lung cancer. Smog is well known for causing irritation in the eye. It may also result in inflammation in the tissues of lungs; giving rise to pain in the chest.

Other issues or illnesses such as cold and pneumonia are also related to smog. The human body faces great difficulty in defending itself against the harmful effects of smog.

The last level of ‘hazardous’ on the AQI is shown as between 250 to 300 which necessitates the people with heart and lung diseases.