A cold wave is a marked drop in temperature over a large area, caused by the advection (horizontal movement) of very cold air masses from higher latitudes into lower latitudes. It is often accompanied by frost, fog, or strong winds — leading to physiological stress, crop damage, and sometimes death.
According to IMD:
Cold Wave: When minimum temperature is 4.5°C–6.4°C below normal.
Severe Cold Wave: When minimum temperature is
>6.4°C below normal, or
≤ 4°C in plains, or
≤ 0°C in hilly areas.
🌀 Mechanism / Causes of Cold Waves
Causative Factor
Explanation
1️⃣ Transport of Cold Air
Cold continental air from higher latitudes moves southwards into India, especially during winter months.
Strengthens easterlies, allowing cold Siberian air to penetrate further south.
4️⃣ Radiational Cooling
Clear skies and calm winds at night enhance terrestrial radiation loss → sharp fall in surface temperature.
5️⃣ Low Pressure over Arabian Sea
In rare cases, easterlies north of such systems transport cold air into NW India.
🌍 Spatial Distribution Pattern in India
Region
Characteristics / Impact
Northern India (Punjab, Haryana, Rajasthan, UP, Bihar)
Most affected. Minimum temperature often drops below freezing. Cold waves peak in Dec–Jan.
Indo-Gangetic Plains
Experience combined effect of cold wave + fog.
Central India (MP, Chhattisgarh)
Occasionally affected when cold winds penetrate southward.
Peninsular India
Rarely experiences cold waves due to maritime moderation and proximity to the equator.
Himalayan States
Cold conditions normal, but frostbite and hypothermia common.
Why extreme cold in North India?
1️⃣ Continental location (far from sea). 2️⃣ Snowfall in Himalayas → cold air descends to plains. 3️⃣ Influx of cold winds from Caspian Sea and Turkmenistan via NW passes (Feb peak).
🩺 Associated Health Hazards
Term
Meaning
Wind Chill
Perceived temperature due to combined effect of wind & cold. Wind removes body heat faster than calm air.
Frostbite
Freezing and tissue damage of exposed body parts (fingers, toes, ears).
Hypothermia
Body temperature drops below 35°C (95°F) → risk of death if untreated.
– Follow District Crop Contingency Plans. – Provide light irrigation to reduce frost formation. – Prune frost-damaged plant parts. – Burn leaves/waste to create smoke & reduce radiation loss. – Use foliar fertilizer sprays and resistant varieties.
Public Health & Shelter
– Convert schools/public halls into shelters for vulnerable groups. – Ensure blankets, heating arrangements, & hot food. – Special outreach for elderly, children, and sick persons.
Infrastructure & Utilities
– Insulate water pipes and critical installations to prevent freezing. – Maintain power supply for heating and water pumping.
Community Preparedness
– Promote awareness through SHGs, PRIs, and NGOs. – Encourage early warning use from IMD bulletins. – Train volunteers for first aid in frostbite/hypothermia.
🧩 Existing Challenges
1️⃣ Localised nature — No uniform national plan; mitigation must be state/district-specific. 2️⃣ Low community participation — Weak coordination with PRIs, SHGs. 3️⃣ Lack of anticipatory preparedness — Reactive rather than preventive action. 4️⃣ Data gap on cold-related deaths — Underreporting and poor record-keeping. 5️⃣ Urban exposure — Homeless populations and inadequate shelter planning in cities.
🧠 Conceptual Contrast: Heat Wave vs. Cold Wave
Aspect
Heat Wave
Cold Wave
Season
Apr–Jun
Nov–Feb
Pressure System
High pressure ridge (subsiding warm air)
High pressure ridge (descending cold air)
Dominant Winds
Hot, dry continental
Cold, dry continental
Health Impact
Heat stroke, dehydration
Hypothermia, frostbite
Affected Region
NW, Central, E. India
N, NW, Indo-Gangetic
Mitigation
Cool roofs, green cover, early warning
Shelter, smoke irrigation, insulation
NDMA Priority
National HAPs (city-based)
Localised frost management plans
📚 Cold Wave Criteria — IMD “Mercurial Meter”
Basis
Condition
Category
Departure from Normal Minimum Temp
4.5°C – 6.4°C below normal
Cold Wave
>6.4°C below normal
Severe Cold Wave
Actual Minimum Temp (Plains)
≤ 4°C
Cold Wave
≤ 0°C
Severe Cold Wave
Actual Minimum Temp (Hills)
≤ 0°C
Cold Wave
≤ –4°C
Severe Cold Wave
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