Delhi's humidity mystery explained: What's behind the second most humid monsoon in 53 years?

Delhi rains

An analysis of historical weather data has revealed that Delhi is currently experiencing its second most humid monsoon season in at least 53 years, compounding the misery of what is already an exceptionally wet period for the capital.

The city has been drenched by 524 mm of rainfall up to August 19, a figure that stands 40% above the normal level and ranks this as the 18th rainiest monsoon since 1901, the HT reported. However, the palpable, oppressive mugginess in the air has a startling statistical backbone.

According to data acquired by HT for the Safdarjung weather station in Delhi from private weather company meteologix.com,, the average relative humidity from June 1 to August 18 this monsoon has reached 76.5%. This is the second-highest average for this 79-day period since 1973, surpassed only by the 78.1% recorded in 2008. It also represents a significant deviation from the recent 1991-2020 average of 67.2% for the same window.

The past week has been particularly gruelling, setting a record for humidity. The average for the five days ending August 18 soared to 89.2%, which is 1.14 times the historical average and the highest ever recorded for those specific dates.

The discomfort felt by residents is a direct result of this atmospheric saturation. High humidity prevents the body from cooling itself effectively through perspiration, a process that also requires somewhat elevated temperatures to function. This leads to a heightened perception of heat and a greater risk of heat-related illnesses.

The primary driver of this unusual humidity has been the monsoon's behaviour. While June was relatively dry in Delhi itself, an early onset of the monsoon over peninsular and north-eastern India pushed moisture inland. By the third week of June, the capital was encircled by the monsoon system, causing humidity to spike even before the official arrival of rains on June 29.

The subsequent months of July and August have been exceptionally rainy. Delhi saw rainfall on all but eight days in July and on all but four days so far in August, providing constant moisture that saturates the air. The HT report noted that humidity’s departure from the norm spiked on days of intense rain. The lingering moisture on days with little to no rain, however, is what creates the peak of discomfort, as temperatures remain high without the relieving effect of a downpour.

The India Meteorological Department does not publicly publish long-term relative humidity data, making this analysis of data from the Safdarjung weather station a unique insight into the capital's stifling season.