EnvironmentSaturday, 30 May 2026·The Hindu - National
IMD’s June 2026 Kerala monsoon onset forecast and the 60% station rule
IMD said on June 1, 2026 that the southwest monsoon is likely to reach Kerala around June 4, after missing its May 26 forecast window.
Key highlights
Direct fact
On June 1, 2026, the India Meteorological Department (IMD) said the southwest monsoon was likely to set in over Kerala around June 4, after its May 15 forecast of May 26 missed the operational window.
Key specifics
- IMD’s May 15, 2026 forecast had predicted Kerala onset on May 26, with a model error of ±4 days.
- The June 4 estimate goes beyond the upper bound of that window, which ended on May 30.
- IMD declares onset only after May 10 when at least 60% of 14 designated stations record 2.5 mm rain for 2 consecutive days.
- Among the stations named are Thiruvananthapuram, Kochi, Kozhikode and Mangaluru.
- Other onset conditions include westerly winds up to about 600 hPa and outgoing longwave radiation below 200 W/m².
Exam lens
Question type: Environment and climate match-the-following, IMD onset criteria, 60% of 14 stations, 2.5 mm rainfall, 600 hPa and 200 W/m² are the key MCQ hooks for a TNPSC one-liner on monsoon onset over Kerala.