Hydro-Meteorological Disasters – II

Drought · Heatwave & Cold Wave · Extreme Weather · Wildfire · Lightning · Cloudburst

📄 GS Paper 3🎯 Prelims + Mains⏱ 17 min read📅 Updated June 2026

Drought: A Creeping, Slow-Onset Disaster

Drought is the most insidious of all hazards — a slow-onset, "creeping" disaster with no clear start or end date, vast spatial spread and cascading effects on water, agriculture, livelihoods and migration. With roughly 68% of India's cultivable area drought-vulnerable and the country's heavy dependence on a four-month south-west monsoon, drought management is a perennial GS3 theme.

Crucially, drought is a function of demand outstripping supply of water over a sustained period — it is therefore both a natural and a socio-economic phenomenon, deeply shaped by cropping patterns, groundwater over-extraction and water governance.

Why drought is unique: Unlike a cyclone or earthquake, drought has no single epicentre or moment of impact. Its onset is gradual, its end is ambiguous, and its damage (crop loss, fodder scarcity, distress migration, debt) accumulates silently — making early declaration and relief politically and technically difficult.

The Four Types of Drought

Drought progresses as a chain — a rainfall deficit (meteorological) cascades into reservoir/groundwater depletion (hydrological) and soil-moisture stress (agricultural), finally producing human distress (socio-economic).

Type	Definition	Key Indicator
Meteorological	A prolonged period of deficient rainfall relative to the long-term normal over an area	Rainfall departure (% from normal)
Hydrological	Depletion of surface and sub-surface water — falling reservoir, river and groundwater levels	Reservoir storage, streamflow, water-table
Agricultural	Insufficient soil moisture to meet crop water demand, harming yields	Soil moisture, NDVI, sown area
Socio-economic	Water shortage impacting supply of economic goods (food, fodder, drinking water) and livelihoods	Distress migration, wages, food/fodder prices

Figure 1: The four types of drought form a cascade — meteorological → hydrological → agricultural → socio-economic.

Causes, Classification & the Revised Drought Manual 2016

Causes of Drought in India

Monsoon failure / weak south-west monsoon: The single biggest driver — over half of India's net sown area is rain-fed.
El Niño (ENSO): El Niño years are strongly correlated with deficient Indian monsoons (e.g., 2009, 2015).
Indian Ocean Dipole (IOD): A negative IOD suppresses monsoon rainfall, while a positive IOD can offset an El Niño.
Anthropogenic factors: Deforestation, over-extraction of groundwater, water-intensive cropping (paddy/sugarcane in arid belts), siltation of reservoirs and poor watershed management.

IMD Rainfall Categories

The IMD classifies seasonal/annual rainfall by its departure from the Long Period Average (LPA):

Category	Departure from Normal (LPA)
Large Excess	+60% or more
Excess	+20% to +59%
Normal	+19% to −19%
Deficient	−20% to −59%
Scanty	−60% to −99%
No Rain	−100%

Prelims hook: A monsoon season is termed a "deficient" / "drought year" at the all-India level when seasonal rainfall is below 90% of LPA (i.e., a deficit greater than 10%). At a station/region level, IMD uses the deficient (−20% to −59%) and scanty (−60% to −99%) categories above.

Manual for Drought Management, 2016 (Revised)

The Department of Agriculture, Cooperation & Farmers' Welfare issued a revised Drought Manual in 2016 to make drought declaration objective, transparent and uniform across states — a key reform from the older, discretionary system.

Did away with the old subjective categories: The earlier practice of declaring a "drought of moderate / severe intensity" on largely discretionary grounds was replaced.
New classification — "Normal", "Moderate", "Severe": Drought is now graded using a structured set of indices rather than ad-hoc declarations.
Mandatory indicators (trigger): Rainfall deficiency and its distribution are the first mandatory trigger.
Impact indicators (four categories): Once triggered, states assess (1) agriculture, (2) soil moisture, (3) hydrology, and (4) remote-sensing (crop health/NDVI) indices.
Ground-truthing / sample survey confirms severity before a formal declaration and SDRF/NDRF assistance.
Timeline: States must declare drought within a defined window (by end-October for kharif) to enable timely relief.

Why it matters for Mains: The 2016 Manual shifted India from reactive, discretionary drought relief toward a rule-based, data-driven, "left of the bang" system — though disputes between Centre and states over declaration and SDRF/NDRF release persist.

Heatwave: The Silent Killer

Heatwaves have become one of India's deadliest recurring hazards, killing thousands and stressing health, power and water systems. Climate change is increasing their frequency, intensity and duration, with summers regularly breaching records across the Indo-Gangetic plains, central India and even the hills and coasts.

IMD Criteria for Declaring a Heatwave

IMD declares a heatwave on two grounds — an absolute temperature threshold and a departure from normal.

Region / Basis	Heatwave Threshold
Plains	Maximum temperature ≥ 40°C
Hilly / Hill regions	Maximum temperature ≥ 30°C
Coastal areas	Maximum temperature ≥ 37°C
Departure-based — Heatwave	Departure from normal of +4.5°C to +6.4°C
Departure-based — Severe Heatwave	Departure from normal of ≥ +6.5°C
Absolute — Severe Heatwave	Actual max temperature ≥ 47°C

Note: The above criteria apply when the actual max temperature reaches at least 40°C (plains) / 30°C (hills) / 37°C (coast). A heatwave is declared when these are met at at least 2 stations in a meteorological sub-division for at least 2 consecutive days.

Heat Action Plans (HAPs) — The Ahmedabad Model

Ahmedabad HAP (2013): Asia's first city-level Heat Action Plan, launched after the deadly 2010 heatwave; credited with saving over 1,000 lives a year through an early-warning colour-code system, public awareness, training of health staff and "cool roofs."
Spread: Following the Ahmedabad model, NDMA has helped roll out HAPs across heatwave-prone states and dozens of cities and districts.
Core components: Early-warning & inter-agency coordination, public awareness (do's and don'ts), capacity-building of health systems, and adaptive/long-term measures (urban greening, water points, work-hour shifts).

Should Heatwave Be a "Notified Disaster"?

Key debate (very high-yield): Heatwave is currently NOT among the 12 notified disasters eligible for SDRF/NDRF funding (the notified list includes cyclone, drought, earthquake, fire, flood, tsunami, hailstorm, landslide, avalanche, cloudburst, pest attack, frost & cold wave). States like Andhra Pradesh, Telangana, Odisha and Bihar have repeatedly demanded heatwave's inclusion. The 15th Finance Commission allowed states to use up to 10% of SDRF for locally notified disasters (heatwave can be covered this way), but a formal national notification is still pending.

Figure 2: IMD absolute temperature thresholds for a heatwave by region, plus the departure-based criteria.

Cold Wave & Frost

Cold waves grip north and north-west India in winter (December–February), driven by western disturbances and cold northerly winds, causing deaths (often among the homeless and elderly), crop frost damage and disruption.

IMD Cold Wave Criteria

For plains (when minimum temperature ≤ 10°C): Cold wave = departure of −4.5°C to −6.4°C from normal; severe cold wave = departure of ≥ −6.5°C.
Absolute basis (plains): Cold wave when minimum temperature ≤ 4°C; severe cold wave when minimum temperature ≤ 2°C.
Frost / cold day: A "cold day" is declared when the maximum temperature is well below normal; frost damages standing rabi crops (wheat, mustard, potato, horticulture).

Impact: Punjab, Haryana, Delhi, UP, Bihar, Rajasthan and Jammu & Kashmir bear the brunt — public-health emergencies for the poor and homeless, livestock losses and frost damage to crops. Cold wave and frost ARE among the 12 notified disasters eligible for SDRF/NDRF funding.

Extreme Weather Events

Beyond drought and temperature extremes, India faces a range of severe convective and winter weather phenomena, increasingly intensified by a warming climate.

Event	Description & Indian Context
Thunderstorm & Squall	Intense convective storms with lightning, gusty winds (squall ≥ 29 knots); common pre-monsoon over east & central India (e.g., "Nor'westers"/Kalbaisakhi in Bengal).
Hailstorm	Ice pellets from cumulonimbus clouds; devastates standing crops & horticulture. A notified disaster.
Dust storm	Strong winds lifting dust/sand, common in arid NW India (Rajasthan, Haryana) in summer; reduces visibility, damages crops & structures.
Blizzard	Severe snowstorm with strong winds & low visibility in the high Himalaya; threatens troops, trekkers & remote villages.
Tornado	Violently rotating column of air; rare in India but does occur in eastern/north-eastern India and Bengal.

Many of these are severe convective phenomena increasingly captured by IMD's Doppler radar network and nowcasting under Mission Mausam (2024).

Wildfire / Forest Fire

Forest fires destroy biodiversity, release carbon, degrade catchments and threaten lives & property, especially in the dry summer months. They are a growing concern as temperatures rise and dry spells lengthen.

Causes

Natural: Lightning, high temperatures, dry biomass (e.g., chir-pine needles in the Himalaya which are highly inflammable).
Anthropogenic (the majority): Slash-and-burn cultivation, burning of agricultural residue, careless campfires, intentional fires to promote fresh fodder growth.

Indian Hotspots & Monitoring

Uttarakhand & Himachal: Recurrent large-scale fires in chir-pine forests every summer.
Similipal (Odisha) 2021: One of the most-cited recent wildfire events, affecting a biosphere reserve.
Forest Survey of India (FSI): Runs satellite-based Forest Fire Alert System (using MODIS/SNPP-VIIRS) sending real-time SMS alerts to forest officials.
Policy: Forest fire was added as a recognised hazard in the National Disaster Management Plan (NDMP) 2019; NDMA has issued guidelines and there is a National Action Plan on Forest Fires.

Lightning

Lightning is, surprisingly, the single largest cause of accidental disaster deaths in India — killing roughly 2,000–2,500 people every year, far more than most "headline" disasters. The deaths are concentrated among farmers and rural workers caught in the open during pre-monsoon and monsoon thunderstorms.

Not a notified disaster: Like heatwave, lightning is NOT in the 12 notified disasters for SDRF/NDRF funding — several states (e.g., West Bengal, Odisha, Bihar) have demanded its inclusion.
Early warning — Damini app: Developed by IITM Pune & ESSO, the Damini app issues lightning alerts within a ~20–40 km radius, giving people time to take shelter.
Lightning Resilient India Campaign and state lightning action plans aim to cut deaths through awareness, early warning and lightning arrestors.

Mains angle: Lightning and heatwave both illustrate the gap between a hazard's actual lethality and its institutional recognition — both kill more than many notified disasters yet remain outside the SDRF/NDRF "notified" list, raising questions of funding and accountability.

Figure 3: Updrafts separate charge in a cumulonimbus — positive at the top, negative at the base — until a discharge (lightning) bridges cloud and ground.

Cloudburst

A cloudburst is a sudden, very intense, localised downpour — defined by IMD as rainfall of more than 100 mm per hour over a small area of roughly 20–30 sq km. Such concentrated rain overwhelms drainage and triggers flash floods, landslides and debris flows, especially in the steep Himalaya.

The Himalayan Orographic Mechanism

Warm, moisture-laden monsoon air is forced to rise rapidly up steep Himalayan slopes (orographic lifting).
The air cools, condenses into towering cumulonimbus clouds; strong updrafts hold raindrops aloft, allowing huge accumulation.
When the updraft can no longer support the load, the entire mass dumps at once — a cloudburst.
Steep terrain channels the water into devastating flash floods and landslides in narrow valleys.

Major Indian Cloudburst Events

Leh (Ladakh), 2010: A catastrophic cloudburst killed over 200 people — a landmark Indian cloudburst disaster.
Kedarnath, 2013: Cloudbursts plus heavy rain triggered the Uttarakhand flash-flood disaster (thousands dead).
Amarnath, 2022: A cloudburst near the holy cave killed pilgrims, highlighting risks to mass gatherings in fragile terrain.

Prediction difficulty: Cloudbursts are extremely small-scale and short-lived, occurring over a few sq km in minutes, so they are very hard to forecast with current models. Denser Doppler radar networks, automatic weather stations and AI-nowcasting under Mission Mausam aim to improve lead time. Cloudburst IS one of the 12 notified disasters.

Figure 4: Moist air rises up the slope (orographic lifting), builds a towering cloud, and dumps >100 mm/hr, triggering flash floods.

Figure 5: The four pillars of a Heat Action Plan — early warning, public awareness, health-system capacity and long-term adaptation.

Current Affairs Snapshot (up to June 2026)

Record heat summers (2024–2026): India recorded some of its hottest summers and longest heatwave spells; heat-related deaths and the demand to notify heatwave as a national disaster gained renewed momentum.
Heat Action Plans scale-up: NDMA expanded HAP coverage to hundreds of cities/districts; the focus shifted to implementation, financing and long-term measures (cool roofs, urban greening) beyond paper plans.
Lightning death toll: Lightning remained the leading cause of accidental natural-disaster deaths; states continued to press for its notification, expanding the Damini app and the Lightning Resilient India Campaign.
Mission Mausam (2024): ₹2,000-crore programme to make India "weather-ready" — denser Doppler radars, more AWS and AI-nowcasting to improve cloudburst & thunderstorm prediction.
Drought monitoring: Continued use of the 2016 Drought Manual indices; uneven monsoons (linked to ENSO/IOD swings) kept parts of central/peninsular India under stress; Centre–state disputes over SDRF/NDRF release recurred.
Forest fire seasons: Recurrent large fires in Uttarakhand and the Himalaya; FSI's satellite alert system and the National Action Plan on Forest Fires remained the backbone of monitoring.
DM (Amendment) Act, 2025: Strengthened NDMA/SDMA and mandated a national disaster database — relevant to better hazard data for drought, heatwave and lightning.

Previous Year Questions — Prelims PRELIMS

How to use: Prelims rewards precise thresholds and definitions. Master IMD rainfall & heatwave criteria, the cloudburst definition, the El Niño–monsoon link, and which hazards are/are not "notified disasters."

UPSC Prelims 2014 Concept

Q. With reference to "Indian Ocean Dipole (IOD)" sometimes mentioned in the news while forecasting Indian monsoon, which statements are correct? (IOD is a recurring Prelims theme linked to monsoon performance and drought.)

Key Points to Remember

IOD is the difference in sea-surface temperatures between the western and eastern Indian Ocean.
A positive IOD generally strengthens the monsoon (can offset El Niño); a negative IOD suppresses it (drought risk).
IOD acts alongside El Niño/La Niña (ENSO) in shaping monsoon rainfall.
A deficient monsoon (<90% of LPA) is the trigger for an all-India drought year.

UPSC Prelims 2023 Definitions / Thresholds (representative framing)

Q. Consider the following on IMD's heatwave criteria — which are correct? (Representative Prelims framing; IMD thresholds and the rainfall departure categories are high-frequency factual areas.)

Key Points to Remember

Heatwave thresholds: plains ≥40°C, hills ≥30°C, coastal ≥37°C.
Departure basis: heatwave = +4.5°C to +6.4°C; severe = ≥ +6.5°C; absolute severe ≥ 47°C.
IMD rainfall: Deficient = −20% to −59%; Scanty = −60% to −99% of LPA.
Cloudburst: >100 mm/hr over ~20–30 sq km.

UPSC Prelims 2017 Classification

Q. Which of the following hazards are/are not among the "notified disasters" eligible for SDRF/NDRF assistance? (Prelims regularly tests the notified list and recent exclusions like heatwave & lightning.)

Key Points to Remember

Notified (12): cyclone, drought, earthquake, fire, flood, tsunami, hailstorm, landslide, avalanche, cloudburst, pest attack, frost & cold wave.
NOT notified (nationally): heatwave and lightning — despite their high death tolls.
States may use up to 10% of SDRF for locally notified disasters (15th FC).
Forest fire was added as a recognised hazard in NDMP 2019.

Previous Year Questions — Mains with Model Answer Structures MAINS

How to use: Each model answer is a structured outline. Flesh out each point into 2–3 sentences in the exam. PYQs are covered up to UPSC Mains 2025.

UPSC GS3 2016 12.5 marks · 200 words

Q. "The frequency of cyclones in the Bay of Bengal is higher than in the Arabian Sea; and cloudbursts have caused immense devastation in the Himalayan region. Account for these and discuss measures to mitigate cloudburst-triggered disasters." (GS3 2016 tested cloudburst devastation in the Himalaya.)

Model Answer Structure

Intro: Define a cloudburst (>100 mm/hr over ~20–30 sq km) as a sudden, localised, intense downpour causing flash floods & landslides.
Why the Himalaya: Orographic lifting of moist monsoon air up steep slopes builds cumulonimbus; updrafts hold then dump rain; steep terrain amplifies flash floods.
Devastation: Leh 2010, Kedarnath 2013, Amarnath 2022 — fragile ecology, unplanned hill construction, pilgrim/tourist crowds raise exposure.
Prediction gap: Small spatial/temporal scale makes forecasting very hard with current models.
Mitigation: Denser Doppler radars & AWS, AI-nowcasting (Mission Mausam), slope-stabilisation, regulated hill construction, early-warning & evacuation drills.
Way forward: Carrying-capacity-based regulation of tourism/pilgrimage; community-based early warning.
Conclusion: Combine better science with prudent land-use to shift "left of the bang."

UPSC GS1/GS3 (Drought) 15 marks · 250 words (representative)

Q. Drought has been recognised as a disaster in view of its spatial expanse, magnitude, and impact on vulnerable sections. Discuss the same with reference to the revised guidelines of 2016. (Representative GS framing on drought as a creeping disaster & the 2016 Drought Manual.)

Model Answer Structure

Intro: Drought as a slow-onset "creeping" disaster — vast spread, no fixed start/end, cascading impacts; ~68% of cultivable area drought-vulnerable.
Types: Meteorological → hydrological → agricultural → socio-economic cascade.
Causes: Monsoon failure, El Niño, negative IOD; plus over-extraction of groundwater & water-intensive cropping.
2016 Manual reforms: Objective declaration via mandatory (rainfall) + impact indicators (agriculture, soil moisture, hydrology, remote sensing); ground-truthing; fixed timelines; new "Normal/Moderate/Severe" grading.
Impact on vulnerable: Distress migration, debt, fodder/drinking-water crisis, malnutrition; women & landless worst hit.
Challenges: Centre–state disputes over declaration & SDRF/NDRF release; delayed relief.
Way forward: Crop diversification, micro-irrigation, watershed dev., crop insurance (PMFBY), drought-proofing under MGNREGA.

UPSC GS3 (Heatwave/Lightning) 10 marks · 150 words (representative)

Q. Despite causing among the highest disaster death tolls in India, heatwaves and lightning are not "notified disasters." Examine the issue and suggest a way forward. (Representative GS3 framing on the notified-disaster debate, a recurring current-affairs theme.)

Model Answer Structure

Intro: Note lightning (~2,000+ deaths/yr) and heatwaves are among the deadliest yet are outside the 12 notified disasters.
The funding gap: Non-notified hazards do not automatically qualify for SDRF/NDRF, limiting compensation & mitigation funds.
Current workarounds: 15th FC allows up to 10% of SDRF for locally notified disasters; HAPs (Ahmedabad model) and the Damini app for lightning.
Arguments for notification: High lethality, climate-change driven rise, uniform national response & funding.
Counter-view: Fiscal concerns; difficulty in attribution & verification of heat/lightning deaths.
Way forward: Strengthen HAPs & early warning, expand Damini, build a robust death-attribution database (aided by DM Amendment Act 2025), and revisit the notified list.

⚡ Quick Revision

Drought types: Meteorological → Hydrological → Agricultural → Socio-economic
Heatwave: plains ≥40°C · hills ≥30°C · coast ≥37°C · departure ≥+4.5°C
Cloudburst: >100 mm/hr over ~20–30 sq km
IMD rainfall: Deficient −20 to −59% · Scanty −60 to −99%
Lightning: #1 accidental disaster death cause

📌 Must-Know Facts

~68% of cultivable area drought-vulnerable
Drought Manual: revised 2016 (objective indicators)
Ahmedabad HAP: 2013 (Asia's first)
Leh cloudburst: 2010 · Amarnath: 2022
Forest fire added: NDMP 2019
Damini app: lightning alerts (IITM Pune)

🏛️ Notified vs Not

Notified (12): drought, cloudburst, hailstorm, frost & cold wave (+8 others)
NOT notified: heatwave, lightning
15th FC: 10% SDRF for local disasters
States demand heatwave/lightning notification

✍️ Answer Keywords

"Creeping/slow-onset disaster"
Orographic lifting
El Niño / IOD–monsoon link
Heat Action Plan (Ahmedabad model)
Notified disaster debate
Mission Mausam · nowcasting