The dry monsoon winds of winter outdid themselves yesterday, driving relative humidity to the lowest level in more than two decades for a March day.
At 1pm the hourly reading hit 23 per cent at the Observatory headquarters in Tsim Sha Tsui - a record low for the month since 1986.
In fact, since 1961, that level of dryness has only been surpassed twice in March.
It dipped to 16 per cent on March 4, 1977, and 22 per cent on March 3, 1984.
Yesterday's 23 per cent reading was matched on March 6, 1972, and March 2 and 3, 1986.
Citywide, readings started to drop from 8am yesterday, hitting the lowest point early in the afternoon.
Observatory scientific officer Kok Mang-hin said most of the city had readings of 30 per cent or lower during the afternoon.
The driest areas were Wong Chuk Hang and Tsing Yi, with multiple hourly readings of 12 per cent in the afternoon.
Tsuen Wan experienced 13 per cent for several hours.
Kok said it was normal for the weather to alternate between a dry, cool northeasterly monsoon on the one hand, and a humid, warm maritime airstream on the other - bringing large swings in the city's humidity levels.
"Higher humidities are expected for the coming days, as the monsoon will moderate," Kok said.
Hong Kong experienced unseasonably warm weather in February, with monthly rainfall well below the normal figure of 54.4 millimetres.