Pragnya IAS · Map 20 · Climate & environment
Advancing southwest monsoon: normal onset dates map study
Read the onset isochrones as a travelling front, not a single national date.
STUDY NOTE 1
A travelling front
The monsoon normally reaches Kerala around 1 June, spreads up both coasts, and covers most of the country by mid-July. Isochrone lines mark normal onset dates.
STUDY NOTE 2
Two branches
The Arabian Sea branch strikes the west coast first; the Bay of Bengal branch turns towards the northeast and the northern plains. Their interaction decides regional onset order.
STUDY NOTE 3
Normal is not forecast
Onset dates vary year to year. The map shows climatological normals; actual onset in any year can be early or late by a week or more.
Map reading task
Trace the 1 June, 15 June and 1 July isochrones and explain why the northeast gets rain before Delhi.
Map key · Reference locations
What does this advancing southwest monsoon: normal onset dates lesson explain?
The monsoon normally reaches Kerala around 1 June, spreads up both coasts, and covers most of the country by mid-July. Isochrone lines mark normal onset dates.
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
Pragnya IAS explanations and practice are independently authored. The uploaded geography compilation informed topic selection only; its pages, illustrations, advertisements and personal watermarks are not republished. Licensed base data retain their original attribution. These lessons are educational references, not navigation, legal boundary or live hazard maps.