Context (TH): The India Meteorological Department (IMD) has issued a cold wave warning for several districts in Telangana, highlighting an unusual southward spread of cold-wave conditions. Telangana is also the only South Indian state included in IMD’s core cold-wave zone.
What is a Cold Wave?
A cold wave refers to an abrupt and significant drop in temperature below the normal climatological average of a region during winter.
Role of IMD
The India Meteorological Department monitors winter temperatures and issues colour-coded warnings (Green, Yellow, Orange, Red).
IMD uses minimum temperature thresholds and deviations from the long-term average to classify cold-wave intensity.
Climatological Baseline
Normal winter temperature values are based on IMD’s 1981–2010 climatology dataset.
Criteria for Declaring Cold Wave
1. Plains
Cold wave declared when:
- Minimum temp ≤ 4°C, or
- Minimum temp ≤ 10°C and 4.5°C–6.4°C below normal
2. Hilly Regions
- Minimum temp ≤ 0°C, and 4.5°C–6.4°C below normal
3. Coastal Regions
- Minimum temp ≤ 15°C and ≥4.5°C below normal
Severe Cold Wave
Declared when:
- Minimum temp ≤ 2°C, or
- Temperature is ≥6.5°C below normal
Why Do Cold Waves Occur in India?
1. Western Disturbances
The passage of Western Disturbances brings cold, dry north-westerly winds from the Himalayas and Central Asia.
2. High-Pressure Systems
The Siberian High intensifies and pushes cold continental air masses toward India.
3. Himalayan Snowfall
More snowfall → stronger cold air advection into the northern plains.
4. Clear Skies
Absence of clouds = strong nighttime radiative cooling, causing sharp temperature drops.
5. Dense Fog
Fog blocks daytime solar radiation, worsening cold conditions.
6. La Niña Events
IMD observations show La Niña years bring longer and more intense cold waves.
7. Continental Climate
Interior regions far from the sea lack maritime moderation, making them more vulnerable.
Consequences of Cold Waves
1. Health Risks
- Hypothermia
- Frostbite
- Asthma & COPD exacerbation
- Cardiovascular stress due to vasoconstriction
India records ~824 annual deaths due to cold exposure.
2. Agricultural Losses
- Frost damage to crops
- Reduced livestock productivity
- Stress on horticultural crops during flowering/fruiting
3. Infrastructure & Transport
- Fog-induced delays in rail, road, and air transport
- Power demand surges → outages
- Water pipelines may freeze in northern hill states
About the India Meteorological Department (IMD)
- Established in 1875, IMD is India’s National Meteorological Service.
- Functions under the Ministry of Earth Sciences (MoES).
- One of six Regional Specialized Meteorological Centres (RSMCs) under WMO.
- Provides:
- Meteorological observations
- Weather forecasts
- Disaster warnings for weather-sensitive sectors
Conclusion
Cold waves are a recurring winter hazard in India, driven by large-scale atmospheric circulation, local geography, and global climate patterns.
With rising climatic variability, timely IMD alerts, climate-resilient agriculture, and public health preparedness have become essential for reducing cold-wave impacts.