Hong Kong sweltered in extreme heat on Wednesday, as the observatory logged a maximum temperature of about 33 degrees Celsius in the afternoon, marking the hottest "cold dew" day in the city's history.

According to the forecaster, the "cold dew" solar term refers to the arrival of late autumn, a time when northern regions experience plunging temperatures and frost begin to form.

"However, Hong Kong, being in the south, has not yet felt the coolness of autumn and it is still quite hot," it said in a social media post.

The observatory said this is the fourth day this month that temperatures have reached 33 degrees or above, setting a new record for the highest number of such hot days in October since records began in 1884.

The weatherman is attributing the scorching heat to the influence of an anticyclone aloft, which is bringing hot and dry weather to southern China.

It's expecting the sweltering conditions to remain for a few more days, before the mercury drops slightly early next week.