Monsoon long period average
About 87 cm of rain over the season.
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Normal is 96-104% of the LPA.
Quick recall
- What is the LPA?
- Long period average rainfall used as the benchmark.
- What is the current all-India LPA?
- About 87 cm (1971-2020).
- What range is 'normal'?
- 96-104% of LPA.
- What is 'deficient'?
- Below 90% of LPA.
- What is 'excess'?
- Above 110%.
- What was the earlier LPA?
- About 88 cm (1961-2010).
Asked before in UPSC
Recurring theme: Behaviour and variability of the Indian monsoon
Tests the regional behaviour of the south-west monsoon whose seasonal total IMD measures against the LPA.
The monsoon's dependability relative to its long period average underpins its role in food production.
Seasonal rainfall measured against the long period average is how changing monsoon behaviour is tracked.
IMD forecasts monsoon rainfall as a percentage of LPA and routinely factors El Nino into them.
The basics
Why it matters
The IMD judges the southwest monsoon against its long period average (LPA) rainfall. For 1971-2020, the all-India LPA for June to September is about 87 cm.
Rainfall categories
The IMD classifies seasonal rainfall as a share of the LPA.
You now know
- All-India LPA (1971-2020): about 87 cm for June-September.
- Normal: 96-104% of LPA.
- Deficient: below 90%; excess: above 110%.
- Earlier LPA (1961-2010) was about 88 cm.
Go deeper
In one line: The LPA is the yardstick for calling a monsoon good or bad.
Why it matters for UPSC
Monsoon categories are frequent Prelims facts.
The core idea
A national average can hide regional deficits; see Rainfall distribution and the influence of ENSO and IOD.
Where to go next
- Rainfall distribution: Why regional rain matters
- ENSO and IOD: Ocean drivers of the monsoon
In one line: Normal all-India rain can coexist with regional droughts.
Example
2026: large deficits in some States. See Rainfall distribution and ENSO and IOD.
Where to go next
- Rainfall distribution: Why regional rain matters
- ENSO and IOD: Ocean drivers of the monsoon
Rainfall distribution
Why regional rain matters
In one line: Rainfall distribution is how rain is spread across regions and weeks.
Why it matters
Crops need timely rain; long dry spells harm yields.
Measures
District-level deviation and dry spell counts.
Where to go next
- ENSO and IOD: Ocean drivers of the monsoon
ENSO and IOD
Ocean drivers of the monsoon
In one line: El Niño-Southern Oscillation and the Indian Ocean Dipole are ocean patterns that affect the monsoon.
El Niño
Usually weakens it.
Positive IOD
Usually supports it.
Where to go next
- Rainfall distribution: Why regional rain matters
Prelims-style quiz
A monsoon is 'normal' if rainfall is:
- Above 110%
- 105-110% of LPA
- 96-104% of LPA
- 90-95% of LPA
Show answer
Answer: (c) 96-104% of LPA. 96-104%.
Consider the following:
1. The current LPA is based on 1971-2020.
2. Deficient means below 90% of LPA.
Which of the statements given above is/are correct?- 1 only
- 2 only
- Both 1 and 2
- Neither 1 nor 2
Show answer
Answer: (c) Both 1 and 2. Both correct.
The all-India monsoon LPA is about:
- 87 cm
- 107 cm
- 117 cm
- 67 cm
Show answer
Answer: (a) 87 cm. About 87 cm.
Monsoon forecasts are issued by the:
- CWC
- NDMA
- ISRO
- IMD
Show answer
Answer: (d) IMD. India Meteorological Department.