© SCMP/Hong Kong Environmental Protection Department
Temperatures hit a high of 36 degrees Celsius in Happy Valley as Taiwan felt the full force of the tropical cyclone, which is forecast to bring gloomy weather to Hong Kong over the next six days.
The Environmental Protection Department issued a warning after the Air Quality Health Index in Tuen Mun and Tung Chung hit 10+ on Tuesday afternoon, its highest level. That indicates a serious health risk.
It was the second day the city recorded such severe levels of air pollution.
The index in Central reached 10, and it climbed to nine in Yuen Long and Causeway Bay, indicating a "very high" health risk.
The department advised children, the elderly and people suffering from heart or respiratory illnesses to stay indoors as much as possible.
Typhoon Megi, named after the Korean word for catfish, made landfall in Taiwan but was forecast to spare Hong Kong. The storm however created stifling conditions in the city on Tuesday, with low visibility and a maximum temperature at the Observatory's headquarters of 34.9 degrees, constituting the hottest September day since 1963, when September 5 saw the same location record 35.2 degrees.
Ahead of the heat the Hong Kong Observatory issued a very hot weather warning at 7.17am.
"Tropical cyclone Megi will cross Taiwan today and make landfall over the vicinity of Fujian tomorrow morning. It will then move inland and weaken rapidly," the Observatory said.
It said its subsidence airstream was affecting the Guangdong area and bringing heat and haze to the city. Visibility in places fell to below 3,000 metres on Tuesday morning.
The weather will turn cloudy with showers in the coming six days. The city will see some sun on Wednesday morning at first, but it will become cloudy in the afternoon with a few showers. Temperatures will be between 27 and 32 degrees Celsius.
Thursday is forecast to see cloud and rain, with the sun not returning until next Tuesday.
Megi also disrupted air traffic between Hong Kong and Taiwan on Tuesday.
At least 37 flights between Hong Kong and Taipei were cancelled, while 12 flights to and from Kaohsiung were suspended.
Cathay Pacific and Dragonair alone cancelled 17 flights to and from Taipei and four flights to and from Kaohsiung.
The storm will also disrupt air traffic between Hong Kong, Taiwan and Fujian province on Wednesday.
Cathay Pacific and Dragonair will cancel one flight from Xiamen, while a flight from Kaohsiung and one from Taichung will be delayed.
China Airlines and Mandarin Airlines will cancel four flights between Hong Kong and Kaohsiung and five flights between Hong Kong and Taichung.
The Hong Kong Airport Authority advised passengers to contact their airlines and check the airport website or flight information display screens for the latest updates.
Comment: Temperatures around the world, like the weather, are becoming more extreme. See also: