IMD Monsoon Forecast: How to Read It for Farm Planning
The IMD monsoon forecast is the most watched weather outlook for Indian farmers, yet many people read only the headline number and miss what it really says. IMD, the India Meteorological Department, publishes the monsoon outlook in stages, uses fixed categories such as “below normal” and “deficient”, and measures rain against a long period average of about 87 cm. This guide explains how to read each forecast, what the 2026 season taught us about forecast limits, and how to turn a forecast into a sowing and water plan.
It is a reading guide, not a weather bulletin. For the season’s final numbers, see our monsoon update.
Quick answer: IMD compares forecast rainfall with the long period average (LPA), which is about 87 cm for June to September using 1971 to 2020 data. Below 90 percent of LPA is deficient, 90 to 95 is below normal, 96 to 104 is normal, 105 to 110 is above normal and over 110 is excess. Every forecast carries an error margin, commonly plus or minus 4 percent.
Key takeaways
- The long period average for the southwest monsoon is about 87 cm, based on 1971 to 2020 data.
- IMD issues a first-stage forecast in April, an updated forecast in late May, and monthly outlooks through the season.
- In 2026 the April forecast was 92 percent of LPA, the late-May update was 90 percent, and the season finished at 87 percent.
- A national percentage hides big regional gaps, so always check your own subdivision and district forecast.
- Use the forecast to choose crop, variety and water plan, but keep a backup plan for dry spells.
सारांश (हिंदी): आईएमडी मानसून पूर्वानुमान दीर्घावधि औसत (LPA) के मुकाबले बारिश बताता है, जो करीब 87 सेमी है। 90% से कम बारिश को कमी वाला (डेफिशिएंट), 90 से 95% को सामान्य से कम, 96 से 104% को सामान्य, 105 से 110% को सामान्य से अधिक और 110% से ऊपर को अत्यधिक कहा जाता है। राष्ट्रीय आंकड़े के साथ अपने ज़िले का पूर्वानुमान ज़रूर देखें।
IMD monsoon forecast categories explained
IMD labels the season by how much rain falls compared with the long period average. The categories are fixed, so you can read any year’s forecast the same way.
| Category | Rainfall as % of LPA | What it usually means for farms |
|---|---|---|
| Deficient | Less than 90% | Drought risk; water-saving crops and short-duration varieties |
| Below normal | 90 to 95% | Uneven rain; plan irrigation backup |
| Normal | 96 to 104% | Good conditions for most rainfed crops |
| Above normal | 105 to 110% | Good storage, but flood and waterlogging risk in some areas |
| Excess | More than 110% | Flooding, crop damage and disease pressure |
What the long period average means in the IMD monsoon forecast
The LPA is the average June to September rainfall over a long reference period. For the current series it is about 87 cm, or roughly 868.6 mm, using 1971 to 2020 data. A forecast of 90 percent of LPA therefore means about 78 cm of rain, not “90 cm”.
How IMD issues the monsoon forecast in stages
The forecast is not a single prediction. It is updated as new ocean and atmosphere data arrive, and later updates are usually more reliable than early ones.
| Stage | When | What it tells you |
|---|---|---|
| First-stage forecast | Mid-April | Seasonal rainfall as a percentage of LPA, with a model error |
| Second-stage update | Late May | Updated seasonal forecast, Kerala onset estimate, probabilities of each category and regional outlook |
| Monthly outlook | Start of each month | Rainfall and temperature for the coming month |
| Extended range forecast | Weekly | Rain pattern for the next two weeks |
| Short-range and district alerts | Daily | Rain warnings for the next few days |
Using the 2026 IMD monsoon forecast as a worked example
The 2026 forecasts show why stage and error margin matter.
| Forecast or result | Rainfall as % of LPA | Note |
|---|---|---|
| First stage, 13 April 2026 | 92% | Below normal |
| Second stage, 29 May 2026 | 90% | Below normal; model error of plus or minus 4%; 60% probability of a deficient season |
| Actual season, June to September | 87% | Deficient, the lowest since 2015 |
The season came in lower than even the downgraded forecast, which is why the guidance matters: prepare for the lower end of the range, not the middle.
Why the national IMD monsoon number can mislead
A national percentage is an average. It can hide floods in one region and drought in another, and it says nothing about how rain is spread across the season.
- Regional gaps. In 2026, central India received about 97 percent of normal rain while East and North-East India received about 74 percent and the South Peninsula about 76 percent.
- Timing. A season can reach its total with heavy rain in a few days and long dry gaps in between. Crops suffer in the gaps.
- Intensity. Short, heavy bursts run off and recharge less groundwater than steady rain.
- Local variation. Rain can differ widely between neighbouring talukas.
So after you read the national outlook, always check your own meteorological subdivision and your district forecast.
How to read IMD rain and alert terms
IMD uses standard words for daily rain. Knowing them lets you act on a warning properly.
| Term | Rain in 24 hours |
|---|---|
| Light | 2.5 to 15.5 mm |
| Moderate | 15.6 to 64.4 mm |
| Heavy | 64.5 to 115.5 mm |
| Very heavy | 115.6 to 204.4 mm |
| Extremely heavy | 204.5 mm or more |
What the colour alerts mean
- Green: No warning. Carry on normally.
- Yellow: Be aware. Weather may disturb work in the field.
- Orange: Be prepared. Harvest, cover and move produce and drain fields.
- Red: Take action. Severe weather is expected.
How to use the IMD monsoon forecast for farm planning
Turn the forecast into decisions. The table gives a simple link between the outlook and common farm choices. It is a general guide, so ask your local agriculture office for advice suited to your district.
| If the outlook is | Consider |
|---|---|
| Deficient or below normal | Short-duration and drought-tolerant varieties, pulses and oilseeds in place of water-hungry crops, mulching, drip or sprinkler, and a water budget for the rabi season |
| Normal | Regular sowing calendar, balanced fertiliser, standard varieties, and some irrigation backup for dry spells |
| Above normal or excess | Good drainage, raised beds, flood-tolerant varieties, careful storage and disease watch |
A simple weekly routine in the monsoon
- Read the national and state outlook once a month.
- Check your district forecast every few days during sowing.
- Delay sowing if heavy rain is forecast within two to three days, since seed can wash out.
- Time spraying and fertiliser for dry windows so they are not washed away.
- Record rain in your own field with a simple rain gauge.
Use our crop calendar for sowing windows, our kharif season guide for crop choices, and the fertilizer calculator to avoid waste. For price signals, see Kharif MSP 2026-27 and Rabi MSP 2026-27.
Where to find the official IMD monsoon forecast
- IMD website and Mausam app: seasonal, monthly and district forecasts, plus warnings.
- Meghdoot app: agro-meteorological advisories for farmers.
- Local agricultural university or Krishi Vigyan Kendra: district advisories you can act on.
- State agriculture department: crop plans and contingency measures.
Be careful with unverified forecast posts on social media. A viral “monsoon prediction” is not an IMD forecast, and it may use made-up numbers.
Common mistakes when reading the IMD monsoon forecast
- Treating the first-stage forecast as final when it is updated in May.
- Ignoring the error margin and the probability of a deficient season.
- Reading only the national figure and forgetting regional gaps.
- Confusing “90 percent of LPA” with “90 cm of rain”.
- Planning only for a normal year and having no backup for dry spells.
IMD monsoon forecast: the bottom line
Read the category, the stage and the error margin together, then check your own district. Plan for the lower end of the range, build in a water reserve and choose varieties that can handle a dry gap. A good plan works in a normal year and still protects you in a poor one.
Follow current coverage in Agriculture News, see how weather affects markets in agri stocks, or return to the Harvest homepage.
Data note: forecast categories, the 2026 forecast values and the LPA come from IMD announcements as reported in May 2026, and the season result comes from IMD’s 30 September 2026 summary. Forecast products and dates can change. The Harvest is an independent information website and is not affiliated with IMD or any government body.
IMD monsoon forecast: frequently asked questions
What does LPA mean in the IMD monsoon forecast?
LPA means long period average, the average June to September rainfall over a reference period. For the current series it is about 87 cm, using 1971 to 2020 data.
What are the IMD monsoon forecast categories?
IMD calls rainfall deficient below 90 percent of LPA, below normal at 90 to 95, normal at 96 to 104, above normal at 105 to 110 and excess above 110 percent.
When does IMD issue the monsoon forecast?
IMD issues a first-stage forecast in mid-April, an updated forecast in late May, monthly outlooks at the start of each month, and weekly and daily forecasts during the season.
How accurate was the IMD forecast in 2026?
The April forecast was 92 percent of LPA and the late-May update was 90 percent with a model error of plus or minus 4 percent. The season ended at 87 percent, lower than both forecasts.
What do IMD colour alerts mean?
Green means no warning, yellow means be aware, orange means be prepared and red means take action because severe weather is expected.
Why can the national monsoon number mislead farmers?
It is an average. In 2026 central India received about 97 percent of normal while East and North-East India received about 74 percent, so local and district forecasts matter more for planning.
Where can farmers get official IMD monsoon information?
Use the IMD website and the Mausam app for forecasts and warnings, and the Meghdoot app, your Krishi Vigyan Kendra or state agriculture department for farm advisories.
