Pragnya IAS · Map 43 · Climate & environment
Normal dates of onset of the southwest monsoon map study
Practise the isochrone map until you can place the 1 June, 15 June, 1 July and 15 July lines from memory.
STUDY NOTE 1
The classic sequence
Kerala coast ~1 June; Mumbai and the northeast ~5–10 June; Bengal and central India ~15 June; Delhi ~end June; Rajasthan covered by ~1–15 July.
STUDY NOTE 2
Why the northeast leads
The Bay branch is trapped by the Arakan hills and Himalayan wall, so Assam and Bengal get onset before the northern plains despite being farther east.
STUDY NOTE 3
Onset versus withdrawal
Onset races north in about six weeks; withdrawal from the northwest takes from September into October — the asymmetric monsoon calendar.
Map reading task
Draw the four key isochrones and annotate one city on each with its normal onset date.
Map key · Reference locations
What does this normal dates of onset of the southwest monsoon lesson explain?
Kerala coast ~1 June; Mumbai and the northeast ~5–10 June; Bengal and central India ~15 June; Delhi ~end June; Rajasthan covered by ~1–15 July.
UPSC map practice & Geography Optional connection
For UPSC Prelims, pair the location with its state, neighbouring relief and relevant geographic process. For GS I and Geography Optional Indian geography revision, use a simple labelled sketch to explain the relationship rather than replacing the answer with place names. These are Pragnya-authored exercises, not official UPSC previous-year questions.
References & map credits
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