NEW DELHI -- New Delhi plans for the first time to make rain to try improve air quality in the city, which is the world's most polluted capital and has been gripped by smog for a week.

The city has already shut all schools, stopped construction activities, and said it will impose restrictions on vehicle use.

Depending on legal approval and weather conditions, the local environment minister said authorities would try to induce rain from around Nov. 20 without specifying how it would be done.

Air quality deteriorates every year ahead of winter, when cold air traps pollutants from sources including vehicles, industries, construction dust, and agricultural waste burning.

"There is a possibility that, if current weather conditions persist, then this week or till some time in the future the pollution situation will remain the same," Delhi's Environment Minister Gopal Rai told reporters.

Rai said a proposal drafted by experts on making rain will be presented to the Supreme Court on Friday.

"I believe that given the conditions we have and if we get support from everyone, we can do the first pilot at least," Rai said.

China, Indonesia and Malaysia have previously induced rain, including by seeding cloud and releasing chemicals into the air.

The air quality index for the city was over 320 early on Wednesday, a level categorized as "hazardous" by Swiss group IQAir, before falling to 294 later.

The local government issued a notice earlier in the day to close all government and private schools from Thursday until Nov. 18 on a winter break, which was originally scheduled for January.

As air quality worsened in the last week, the Supreme Court ordered states surrounding New Delhi on Tuesday to stop farmers burning crop residue.

(Reporting by Shivam Patel, additional reporting by Manoj Kumar, writing by Shilpa Jamkhandikar; Editing by Raju Gopalakrishnan and Barbara Lewis)