Temperatures are expected to dip to 26 degrees Celsius in the next couple of days amid a fresh easterly airstream, with low pressure bringing showers to Guangdong, the Observatory says.
The weather will improve from Friday as an anticyclone is expected to affect Guangdong.
"Sunny intervals and a few showers on the Mid-Autumn Festival and the day after are expected as the anticyclone aloft weakens," the Observatory said.
The very hot weather warning was on until 5.45 pm yesterday - 59 hours after it was hoisted on Sunday.
Yesterday, the Observatory's headquarters in Tsim Sha Tsui recorded 35.3 degrees, which is the hottest day in September since 1884.
"The level of humidity is also expected to rise to 75 to 95 percent in the next couple of days," it said after relative humidity of 38 percent was felt yesterday.
Clouds with occasional showers and one or two thunderstorms, with moderate to fresh winds, are expected today and tomorrow, with temperatures ranging from 26 to 30 degrees.
But the weatherman expected temperatures to rise to 32 degrees on Friday. Mainly cloudy weather is expected throughout the Mid-Autumn Festival weekend, with sunny intervals during the daytime.
A tropical cyclone over the western north Pacific east of the Philippines will linger over the region in the next couple of days.
The cyclone is expected to move to Okinawa, Japan, where it may develop into a severe tropical storm or a typhoon.
Meanwhile, super typhoon Hinnamnor landed in Geoje, South Korea, yesterday, bringing gale-force winds reaching 40 meters a second. More than 66,000 households encountered a blackout.