Not the first time that monsoon has missed date with Kerala. Check previous instances

An analysis of monsoon rains in the ten years when it started over Kerala this late shows that it is no guarantee of a surplus or deficit.

Thursday, June 8, is not the only instance that the monsoon has played truant for a week.

Dark clouds cover the city skyline during the onset of monsoon over Kerala a week later than usual, in Kochi, Thursday, June 8, 2023.(PTI)

There have been ten other years since 1971 when the monsoon arrived on or after June 8, with 2019 being the only year when the monsoon arrived exactly on June 8. The onset over Kerala was on June 9 in 1996 and 2002; on June 10 in 1995; on June 12 in 1979, 1983, 1986, and 1997; on June 13 in 2003; and June 19 in 1972.

HT analysed data only since 1971 because onset dates by the new objective criteria in use since 2006 were available only as far back as 1971. These reworked onset dates from 1971 to 2005 were calculated retrospectively by climate scientists DS Pai and Rajeevan M Nair for their research paper “Summer monsoon onset over Kerala: New definition and prediction".

Read: Number theory: How have El Nino and delayed onset affected monsoon in the past

An analysis of monsoon rains (total rain over India in the normal monsoon months of June to September) in the ten years when it started over Kerala this late shows that it is no guarantee of a surplus or deficit. There was a surplus and deficit in five years each compared to the 1961-2010 average, the benchmark for this period. This was also true for June rain, although not necessarily in the same years. The deficit was 10% or bigger -- the criteria for the deficit to be classified as "deficient" -- overall in three years and in June in four years.

Read: Monsoon rain reaches Kerala after longest delay in 4 years

To be sure, the monsoon was also affected by El Nino in five of the ten delayed onset years. Three of these five years coincide with the five years of deficit rains in June and June-September (not necessarily the same three years for both).

El Nino is a warming of the equatorial Pacific Ocean that is associated with a dry southwest monsoon over the Indian subcontinent. It is expected to take place during the 2023 monsoon season.