Long Period Average
In one line: The Long Period Average (LPA) is the average rainfall over a long base period, used as the benchmark to judge whether a monsoon season is normal, deficient or in excess.
The numbers
IMD's current LPA for the June to September season for the country as a whole is about 87 cm, based on the period 1971 to 2020. A country-wide season is 'normal' at 96% to 104% of the LPA, 'below normal' at 90% to 95%, 'deficient' below 90%, 'above normal' at 105% to 110% and 'excess' above 110%.
Area-level categories
For a district or subdivision, IMD uses departures from its own normal: -19% to +19% is normal, -20% to -59% deficient, -60% to -99% large deficient, and +20% or more excess.
Why it is in the news
By 19 September 2026, all-India rainfall was 15% below normal and nearly 43% of the country's area was deficient.
Where to go next
- Retreating monsoon
- Low-pressure systems in the Bay of Bengal
Long Period Average in the news
- Monsoon begins withdrawing from west Rajasthan with 43% of India's area rain-deficient 20 September 2026
The benchmark that decides whether a season is normal.
- India records its hottest August since 1901; IMD forecasts below-normal September rain 1 September 2026
How IMD defines normal rainfall
Previous-year questions on this
- 2017 · GS1 · 15 marks What characteristics can be assigned to monsoon climate that succeeds in feeding more than 50 percent of the world population residing in Monsoon Asia?
- 2015 · GS1 · 12.5 marks How far do you agree that the behaviour of the Indian monsoon has been changing due to humanising landscape? Discuss.
- 2014 · GS3 · 12.5 marks Drought has been recognised as a disaster in view of its spatial expanse, temporal duration, slow onset and lasting effect on various vulnerable sections. With a focus on the September 2010…
- 2017 · Prelims With reference to 'Indian Ocean Dipole (IOD)' sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct? 1. IOD phenomenon is characterised…