India, July 3 -- The India Meteorological Department (IMD) declared the onset of monsoon over Delhi on July 2, as well as parts of Uttar Pradesh and Madhya Pradesh it had not covered by July 1, apart from making further progress in Punjab, Haryana, Gujarat, and Rajasthan. At least in Delhi, the declaration of monsoon onset may not have appeared to square with reality since the rain hardly had any intensity. How did the IMD declare monsoon onset over Delhi then? Here are three charts that try to make sense of this.

That Delhi did not receive much rain on the day IMD declared monsoon onset over Delhi can be seen by looking at the rainfall different weather stations in Delhi received in the 24 hours ending 08:30 AM on July 2, the standard 2...