India, Dec. 27 -- A persistent patter of rain that continued through Friday to soak Delhi and its surrounding regions, delivering an unusually wet December day that shattered long-standing rainfall records and highlighted the unpredictability of the season.

By the end of the day, the city had recorded 42.8mm of rainfall this month, making it the fifth wettest December in Delhi's recorded history and the rainiest since 1997, or in 27 years, according to data from the India Meteorological Department (IMD).

The rainfall, largely attributed to an active western disturbance interacting with easterly winds, transformed the usual dry chill of December into an anomaly.

Safdarjung, Delhi's primary weather observatory, recorded 30.2mm of rain in...