The mean temperature for June was 29.7 degrees Celsius, 1.8 degrees above normal, making it the hottest June in Hong Kong since records began in 1884.
The previous record of 29 degrees was set in June 2014.
The mean minimum temperature of 27.7 degrees and mean maximum temperature of 32.3 degrees also ranked the highest for June.
The extremely hot weather in the month was partly attributed to the westward extension of the subtropical ridge of high pressure from the western North Pacific to southern China, the Hong Kong Observatory said.
The prevailing southerly flow and the above-normal sea surface temperature over the northern part of the South China Sea also contributed to the sweltering weather, it added.
Under the dominance of the subtropical ridge, June was also sunnier and drier than usual.
The total duration of sunshine in the month was 192.8 hours, 46.7 hours above normal while total rainfall was 291mm, 36% below normal.
The accumulated rainfall of 970.6mm since January was 12% below normal.
