A cold wave in India is a spell of abnormally low minimum temperatures that the India Meteorological Department declares only when set numerical thresholds are crossed. On the plains, a station qualifies when its night temperature falls 4.5°C or more below normal, or drops to 4°C or less outright. Cold waves strike mostly between December and February, across a belt of 17 states and union territories from Jammu and Kashmir to Telangana, and the National Disaster Management Authority counts 4,712 deaths from them between 2001 and 2019.
Most readers treat any bitterly cold day as a cold wave. The term is narrower than that. A cold wave is judged on the night’s minimum temperature, while a foggy, sunless day that never warms up is a separate event that IMD calls a cold day, judged on the maximum temperature. A third set of numbers, used only to release disaster relief, differs from both. This note keeps the three apart and then follows the cold into hospitals, fields and the action plans states are now asked to write.
What counts as a cold wave
A cold wave is a defined weather event, not a feeling. IMD uses two tests, one based on how far the minimum temperature falls below its normal and one based on how low it falls in absolute terms. NDMA’s 2021 guidelines reproduce them along with a gatekeeping condition: no cold wave is declared unless the minimum is already 10°C or less in the plains or 0°C or less in the hills.
| Fact | Detail |
|---|---|
| What is measured | Minimum (night) temperature at a station |
| Precondition | Minimum of 10°C or less in the plains, 0°C or less in the hills |
| Cold wave by departure | 4.5°C to 6.4°C below normal |
| Severe cold wave by departure | More than 6.4°C below normal |
| Cold wave by actual value (plains) | Minimum of 4°C or less; severe at 2°C or less |
| Coastal stations | Departure of 4.5°C or more below normal, with the minimum at 15°C or less |
| Season | November to March, with most extreme events in December to February |
| Core cold wave zone | 17 states and union territories, home to 90.90 crore people (Census 2011) |
| Nodal ministry | Ministry of Agriculture, for cold wave and frost |
The departure test is relative, and that is the clever part. A minimum of 8°C would be routine in Amritsar in January but alarming in Hyderabad, so IMD compares each station with its own normal. The absolute test catches the opposite case: on the plains, 4°C is dangerous whatever the normal says.
Cold day vs cold wave
A cold day is the daytime twin of a cold wave, and the two can happen separately. IMD declares a cold day when the maximum temperature falls 4.5°C to 6.4°C below normal, and a severe cold day when it falls more than 6.4°C below, provided the minimum is also 10°C or less on the plains. A cold wave says the night was abnormally cold. A cold day says the afternoon never recovered.
The usual cause of a cold day on the Indo-Gangetic plains is a thick blanket of fog or low cloud that keeps sunlight from reaching the ground. The night under that blanket may not be extreme, because cloud also traps outgoing heat, so a place can log a cold day without a cold wave. The reverse is just as common: a clear, dry night after a western disturbance lets the ground lose heat freely, producing a cold wave, and the following afternoon may warm up normally in bright sunshine.
| Point | Cold wave | Cold day |
|---|---|---|
| Temperature judged | Minimum (night) | Maximum (day) |
| Departure threshold | 4.5°C to 6.4°C below normal; severe beyond 6.4°C | 4.5°C to 6.4°C below normal; severe beyond 6.4°C |
| Absolute test | 4°C or less on the plains; severe at 2°C | None |
| Typical sky | Clear, calm and dry after a western disturbance | Fog or low cloud blocking sunlight |
| Main risk | Hypothermia, frost on crops, livestock deaths | Low visibility, transport delays, prolonged chill |
The pairing explains why one north Indian week can see both. A foggy afternoon gives a cold day, and once the fog lifts a clear night gives a cold wave.
Why cold waves hit north India
Cold waves need cold air, a way to bring it in and conditions that let the ground lose heat. NDMA’s guidelines list five factors behind cold waves over India:
- A ridge in the jet stream over northwest Asia, an elongated zone of high pressure aloft.
- A surface high over north and central India, which brings settled, dry air.
- Cold air masses steered southeastward by the upper-level winds.
- Strong westerly waves approaching northwest India, which speed up the winds carrying cold air.
- Extensive snow cover over the northwest Himalaya, which chills the air that flows off it.
The everyday sequence is easier to remember. A western disturbance passes, bringing rain to the plains and snow to the hills. Behind it the wind swings to the northwest, dry and cold, and the sky clears. NDMA describes exactly this: after western disturbances pass, dry cold northwesterly winds move into north and central India and minimum temperatures drop. The frontal machinery behind the disturbance itself is in the note on air masses and fronts.
NCERT’s chapter on India’s climate gives three reasons for the excessive cold of the northern plains:
- Continentality: Punjab, Haryana and Rajasthan lie far from the moderating influence of the sea.
- Himalayan snowfall: snow in the nearby ranges creates cold wave conditions.
- Northwesterly winds: around February, cold winds from the Caspian Sea and Turkmenistan bring cold wave, frost and fog to northwestern India.
The southern peninsula escapes because the sea and its latitude keep its nights mild. NDMA calls cold wave a localized seasonal phenomenon found across the country except in southern India, though it still lists Telangana in the core zone and some subdivisions of Maharashtra and Gujarat as affected. The wider seasonal picture is in the note on seasons in India.
Is warming making cold waves rarer?
Not in the Indian record so far. NDMA reproduces data from the Indian Institute of Tropical Meteorology in which the average number of cold wave days, summed across 23 states, rose from 59 in 1991-2000 to 75 in 2001-2010 and 86 in 2011-2019. Haryana went from 3 to 9 and Uttar Pradesh from 2 to 6, while Punjab fell from 6 to 3. The guidelines add that warming can make extreme cold more likely in some regions by pushing the circulation into stronger patterns, citing the 2016 East Asian cold wave. A warmer average and a colder extreme aren’t a contradiction.
What a cold wave does
Cold waves kill quietly, mostly through the bodies of people who can’t get warm. NDMA’s figure of 4,712 deaths from 2001 to 2019, drawn from MoSPI’s EnviStats India 2020, makes the cold wave a disaster in the full legal sense, even though it was long treated as ordinary winter. The guidelines name the elderly, infants, the homeless and outdoor workers such as street vendors, rickshaw pullers and daily wage laborers as the most exposed.
The damage spreads across sectors:
- Health: hypothermia, frostbite and a higher burden of respiratory illness; NDMA also warns of carbon monoxide poisoning from charcoal or wood heaters in closed rooms.
- Agriculture: NDMA separates chilling injury, between 2°C and 0°C, from freezing injury below 0°C, and notes that flowering and fruiting stages suffer most.
- Livestock and fisheries: animals need more feed and can die of hypothermia; Indian major carps grow poorly when water stays at 10°C to 15°C.
- Transport and power: fog delays trains and flights, and heating demand pushes up electricity use, especially in the hills.
Frost is the crop end of the same weather. NDMA defines a frost warning for air temperatures below 0°C with light winds. For a farmer in the plains of Punjab or Rajasthan, a clear, still night after a western disturbance can blacken mustard and vegetable crops by morning. The crop calendar these nights cut across is in the note on rabi crops.
How India manages cold waves
India manages cold waves through warnings from IMD, action plans under NDMA’s guidelines and relief through the disaster funds. Each works on different rules.
IMD warnings and color codes
IMD updates its warnings four times a day and runs a special cold wave and fog monitoring report every day from 1 December to 28 February, a multi-agency effort launched in 2016 with NCMRWF, IITM, ISRO and the Indian Air Force. Warnings follow a color scale that NDMA and IMD built around duration as well as intensity:
- Yellow (be updated): cold wave in isolated areas persisting for two days.
- Orange (be prepared): severe cold wave for two days, or cold wave for four days or more.
- Red (take action): severe cold wave for more than two days, or more than six cold wave or severe cold wave days in total.
The duration rule matters. A single bitter night is uncomfortable; the body’s reserves fail over a run of nights, which is why the red alert depends on days as well as degrees. The India Meteorological Department note covers the forecasting system behind these alerts.
NDMA’s 2021 guidelines
NDMA released the National Guidelines for Preparation of Action Plan – Prevention and Management of Cold Wave and Frost in June 2021, noting that until then there were no national guidelines for cold wave. They ask each state to prepare a Cold Wave Action Plan through eight steps, including:
- a cold wave committee chaired by the State Disaster Management Authority;
- a state nodal agency and officer;
- mapping of vulnerable areas and groups with IMD’s help;
- a color-coded local alert system tied to local normal temperatures;
- evaluation and revision after every winter.
Practical measures in the plans include temporary shelters for the homeless with food, water and medicine, and messages in local languages for outdoor workers and slum residents. The three-tier authority structure that carries these plans is explained in the note on NDMA, SDMA and DDMA.
Relief under the disaster funds
Cold wave and frost entered the list of calamities eligible for SDRF and NDRF assistance through a Home Ministry office memorandum dated 13 August 2012, for damage in the agriculture sector. The relief criteria differ from IMD’s forecasting criteria. For relief, severe cold wave means a minimum below 7°C where the normal minimum is 10°C or above, or below 5°C where the normal is under 10°C, and only areas with crop loss of 33% or more qualify, as with drought and hailstorm.
Cold waves today
Cold wave and frost remain a notified calamity for relief, with the Ministry of Agriculture as the nodal ministry, and NDMA’s 2021 guidelines are the standing framework for state plans. Recent winters show how closely seasonal forecasts now track the risk.
IMD’s press release of 1 December 2025 forecast above-normal cold wave days over parts of central, northwest and northeast India for December 2025 to February 2026. It linked the outlook partly to weak La Niña conditions in the Pacific and warned of health risks for vulnerable groups, fog-related transport disruption and poorer urban air quality. By 31 January 2026 the picture had shifted: IMD expected below-normal cold wave days over several parts of northwest and adjoining central India in February 2026, with La Niña likely to give way to neutral conditions. The cool phase’s wider effects are covered in the note on La Niña.
The air-quality link is worth holding onto. The same still, cold air that produces a cold wave also traps smoke near the ground, which is why north Indian winters bring the cold and the smog together, as the explainer on Delhi’s winters and air pollution sets out.
How to study cold wave for exams
Cold wave belongs to two parts of the syllabus. In GS Paper I it sits in climatology, with India’s cold weather season, western disturbances and temperature inversion. In GS Paper III it sits in disaster management, alongside heat waves and the NDMA framework. Prelims pulls the numbers from both, and the site’s Prelims question bank files 82 of its 1,403 questions under Geography and 249 under Environment.
Mains rarely names cold wave directly; it tests the concepts around it. Mains 2013 GS Paper I asked “What do you understand by the phenomenon of ‘temperature inversion’ in meteorology? How does it affect weather and the habitants of the place?” as part (b) of a two-part question on heat islands and inversion, and a cold, clear north Indian night is the textbook inversion. Disaster questions on vulnerability are where the cold wave’s victims, the homeless and outdoor workers, earn marks.
Revise these until they’re automatic:
- 4.5°C to 6.4°C: the departure band for a cold wave; beyond 6.4°C it is severe.
- 4°C and 2°C: the absolute plains thresholds for cold wave and severe cold wave.
- 10°C and 0°C: the preconditions for declaring anything in the plains and the hills.
- Cold day: the same departure band, applied to the maximum temperature.
- 17 states and UTs: the core cold wave zone; 4,712 deaths from 2001 to 2019.
- June 2021: NDMA’s national cold wave and frost guidelines.
- 13 August 2012: cold wave and frost added to SDRF and NDRF relief.
Three confusions cost marks. A cold wave uses the minimum temperature and a cold day uses the maximum. The 7°C and 5°C relief thresholds are not IMD’s forecasting criteria, so don’t mix them in a definition. And cold waves come after western disturbances, not with them; the disturbance brings cloud and rain, and the cold arrives once the sky clears behind it.
| Point | Cold wave | Heat wave |
|---|---|---|
| Season | December to February | March to June |
| Temperature judged | Minimum | Maximum |
| Departure threshold (plains) | 4.5°C to 6.4°C below normal | 4.5°C to 6.4°C above normal |
| Typical trigger | Dry northwesterlies after a western disturbance | Hot, dry winds and clear skies |
| Main victims | Homeless, elderly, outdoor workers | Outdoor workers, elderly, children |
The heat wave’s own criteria and action plans are in the note on heat waves in India, and setting the two side by side is the fastest way to fix both sets of numbers.
The cold wave is a small topic with sharp edges. Learn the four numbers, keep the cold day separate and remember that relief rules use their own thresholds, and you can write an exact definition where most answers settle for “very cold weather”. That precision, plus one line on who dies in a cold wave and why, is what turns a geography fact into a disaster management answer.
Frequently Asked Questions
What is a cold wave according to IMD?
A cold wave is declared when a station’s minimum temperature falls 4.5°C to 6.4°C below its normal, and a severe cold wave when it falls more than 6.4°C below. On the plains a cold wave is also declared when the minimum drops to 4°C or less, and a severe cold wave at 2°C or less. The minimum must already be 10°C or less in the plains or 0°C or less in the hills.
What is the difference between a cold day and a cold wave?
A cold wave is judged on the night’s minimum temperature, while a cold day is judged on the day’s maximum temperature. IMD declares a cold day when the maximum falls 4.5°C to 6.4°C below normal, which usually happens when fog or low cloud blocks sunlight. A place can have one without the other.
Which states are most affected by cold waves in India?
NDMA’s core cold wave zone covers 17 states and union territories, including Jammu and Kashmir, Ladakh, Himachal Pradesh, Uttarakhand, Punjab, Haryana, Delhi, Rajasthan, Uttar Pradesh, Bihar, Madhya Pradesh and Telangana. Jammu and Kashmir records the most cold waves, followed by Himachal Pradesh, Punjab, Bihar, Haryana and Uttar Pradesh.
Why does a cold wave follow a western disturbance?
A western disturbance brings cloud, rain to the plains and snow to the hills. Once it moves east, the winds turn northwesterly, dry and cold, and the sky clears. Cold air flowing off the fresh Himalayan snow, together with clear skies that let the ground lose heat at night, pushes minimum temperatures down to cold wave levels.
Is cold wave a notified disaster in India?
Yes. Cold wave and frost were added to the list of calamities eligible for SDRF and NDRF assistance by a Home Ministry memorandum of 13 August 2012, for losses in agriculture and animal husbandry. The Ministry of Agriculture is the nodal ministry, and areas with crop loss of 33% or more qualify for relief.
What are the NDMA guidelines on cold wave?
NDMA issued national guidelines on the prevention and management of cold wave and frost in June 2021. They ask states to prepare Cold Wave Action Plans with a nodal officer, vulnerability mapping, color-coded alerts, shelters for the homeless and public awareness in local languages, and to review the plan after every winter.
How many people die from cold waves in India?
NDMA’s guidelines, citing MoSPI’s EnviStats India 2020, record 4,712 deaths from cold waves in India between 2001 and 2019. The elderly, infants, the homeless and outdoor workers face the highest risk, mainly from hypothermia and related illness.
Practice Questions
Prelims
1. Consider the following statements about IMD’s criteria for a cold wave in the plains: 1. A cold wave is declared when the minimum temperature departs 4.5°C to 6.4°C below normal. 2. A cold wave is declared when the actual minimum temperature is 4°C or less. 3. A cold wave is judged on the maximum temperature of the day. Which of the statements given above are correct?
- (a) 1 and 2 only
- (b) 2 and 3 only
- (c) 1 and 3 only
- (d) 1, 2 and 3
Answer: (a) Cold waves are judged on the minimum temperature; the maximum is used for a cold day.
2. Consider the following statements: 1. A cold day is declared on the basis of the departure of the maximum temperature from normal. 2. Cold wave and frost are notified calamities eligible for assistance under the State Disaster Response Fund. Which of the statements given above is/are correct?
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Answer: (c) Both are correct; cold wave and frost were added to the SDRF list in August 2012.
3. Cold wave conditions over north India typically set in:
- (a) as a western disturbance approaches, bringing cloud and rain
- (b) after a western disturbance passes, when dry northwesterly winds and clear skies follow
- (c) when the southwest monsoon withdraws in October
- (d) when the easterly jet stream sets in over peninsular India
Answer: (b) NDMA describes dry, cold northwesterlies moving in after the passage of western disturbances.
4. Under IMD’s criteria, a severe cold wave by departure occurs when the minimum temperature is below normal by:
- (a) 2.5°C to 4.4°C
- (b) 4.5°C to 6.4°C
- (c) more than 6.4°C
- (d) more than 10°C
Answer: (c) A departure of 4.5°C to 6.4°C is a cold wave; beyond 6.4°C it is severe.
5. Which one of the following is not among the factors NDMA lists for cold waves over India?
- (a) A ridge in the jet stream over northwest Asia
- (b) Extensive snow cover over the northwest Himalaya
- (c) A surface high-pressure area over north and central India
- (d) An active monsoon trough over the Indo-Gangetic plains
Answer: (d) The monsoon trough belongs to the summer monsoon, not the winter cold wave.
Mains
- Vulnerability is an essential element for defining disaster impacts and their threat to people. How and in what ways can vulnerability to disasters be characterized? Discuss different types of vulnerability with reference to disasters. (15 marks, 250 words) Previous year: Mains 2019, GS Paper III.
- Distinguish between a cold wave and a cold day as defined by the India Meteorological Department. Explain the meteorological conditions that produce each over the Indo-Gangetic plains. (10 marks, 150 words)
- Cold waves were long treated as ordinary winter weather rather than a disaster in India. Examine the shift in this approach and evaluate the NDMA guidelines of 2021 on cold wave and frost. (15 marks, 250 words)
- Discuss the impact of cold waves and frost on agriculture, livestock and public health in north India, and suggest measures to reduce these losses. (15 marks, 250 words)
- Explain why the frequency of cold wave days has not fallen in parts of north India despite a warming climate. (10 marks, 150 words)
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