People were advised not to do outdoor exercises because of hot weather and air pollution. Photo: Hong Kong Observatory

Hong Kong recorded its hottest day of the year on Sunday with an average temperature of 34.8 degrees Celsius, and the highest in Chap Lap Kok, which recorded 37.7 degrees.

At least six males and four females, aged from 17 to 61, reported to police that they had been stricken by heatstroke or felt unwell during hikes in different parts of the New Territories, Sing Tao Daily reported.

At noon, a 19-year-old man, who studies at the University of Hong Kong, suffered heatstroke in Kai Kung Leng in Yuen Long after a three-hour hike. He was in a coma and was sent to North District Hospital, where he was listed in critical condition.

Other people called for police help from Sai Kung, Tung Lung Island, Sharp Island, Tai Po and other areas.

The Observatory issued the “very hot weather” warning, meaning that the risk of heatstroke was high.

Shatin, Sai Kung, Kowloon City, Happy Valley, Wong Tai Sin and Sham Shui Po all hit 37 degrees while Yuen Long, Tai Po, Tseung Kwan O and Stanley recorded 36 degrees on Sunday.

The city also recorded “very high” levels of air pollution in Central and Western District, Kwun Tong and Sha Tin, with “serious” levels in Tuen Mun and Tseung Kwan O.

The Observatory said the high temperatures were due to the outer subsiding air of Typhoon Nesat and Tropical Storm Haitang, and the hot air was mainly from the northwest, where temperatures are generally higher.