EnvironmentSunday, 31 May 2026·The Hindu - Environment
IMD’s June 4 Kerala monsoon forecast: onset criteria, 14 stations and 60% rainfall rule
IMD said on June 1, 2026 that the southwest monsoon is likely to set in over Kerala around June 4, after missing its May 26 forecast window.
Key highlights
Direct fact
In June 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 had projected onset on May 26.
Key specifics
- IMD’s onset forecast was issued on May 15, 2026, with a model error margin of plus or minus 4 days.
- A June 4 onset would be beyond the upper bound of the May 26 forecast window, which ended on May 30.
- IMD declares Kerala onset only after 60% of 14 designated stations record at least 2.5 mm rain for 2 consecutive days.
- The 14-station list includes Thiruvananthapuram, Kochi, Kozhikode and Mangaluru.
- Two meteorological conditions are also required: westerly winds up to about 600 hPa and outgoing longwave radiation below 200 W/m².
Exam lens
MCQ focus: monsoon onset criteria and IMD forecasting, 14 stations, 60% rainfall rule, 2.5 mm for 2 days, 600 hPa and 200 W/m². TNPSC may ask the official conditions for declaring southwest monsoon onset over Kerala.