Haze

Reduced visibility from dry suspended particles — dust, smoke, pollutants — not water droplets. North India and Pakistan suffer severe winter haze.

phenomena

What is Haze?

Haze is reduced visibility caused by dry particles suspended in the air — dust, smoke, sulphates, soot, organic aerosols. It is meteorologically distinct from fog (which is water droplets) and mist (lighter water droplets). Haze can persist for days because the particles don’t readily settle out without rain or strong wind.

Haze is one of South Asia’s most consequential weather and air-quality phenomena. The Indo-Gangetic plain — stretching from Punjab Pakistan through Delhi, UP, Bihar, Bangladesh — experiences some of the world’s worst haze episodes every winter. PM2.5 levels regularly exceed WHO guidelines by 10-30 times, causing premature deaths, respiratory illness, and economic damage on a massive scale.

Haze categories in South Asia

1. Winter pollution haze (November-February) — Indo-Gangetic plain

Stubble burning in Punjab and Haryana
Industrial emissions concentrated by stagnant air
Vehicle exhaust under temperature inversions
Diwali fireworks add an annual peak in late October/early November
Worst affected: Delhi NCR, Lahore, Faisalabad, Patna, Kanpur, Dhaka, Karachi

2. Pre-monsoon dust haze (April-May) — Thar Desert + dry plains

Dust storms (“loo” / “andhi”) whip up Rajasthan, Sindh, southern Punjab dust
Westerly winds transport dust eastward across north India
Visibility drops to 1-3 km for days
Worst affected: Jaisalmer, Bikaner, Jodhpur, Jaipur, Delhi, Lucknow

3. Forest fire haze (March-May) — Himalayan foothills

Uttarakhand, Himachal pine forests burn during dry season
Smoke combines with valley inversions
Worst affected: Dehradun, Shimla, Almora, Nainital

4. Transboundary haze (variable) — from Indonesia/Myanmar

Indonesia peat-fire smoke affects only Southeast Asia (not SA)
Myanmar forest fires occasionally affect Northeast India

Haze vs fog vs smog

These four terms are often confused. The clear distinctions:

Term	Cause	Visibility	Humidity	Health impact
Fog	Water droplets	< 1 km	> 90%	Low (just water)
Mist	Water droplets, lighter	1–5 km	80–90%	Low
Haze	Dry particles (dust, smoke, pollutants)	Variable	< 80%	High (PM2.5)
Smog	Water droplets + pollutants combined	< 1 km	High	Very high

What people in Delhi call “winter fog” is usually smog — the toxic combination of pollution haze and water-droplet fog. Pure dry haze can also be deadly to lungs even at higher visibility.

How haze is measured

Visibility:

Optical sensors at airports and weather stations
WMO category: 1-2 km = thick haze, 2-5 km = moderate haze, 5-10 km = light haze

Particulate matter:

PM2.5 (particles ≤ 2.5 μm) — primary haze indicator
PM10 (particles ≤ 10 μm) — coarser dust
Measured by reference monitors and increasingly by satellite

Aerosol optical depth (AOD):

Satellite-measured atmospheric particulate density
MODIS, INSAT-3D provide regional coverage

On Mausam Online:

Live PM2.5 and PM10 alongside European AQI
Air-quality alerts for severe pollution
Visibility included in standard weather data

Indo-Gangetic plain winter haze

The IGP winter is arguably the most polluted populated region on Earth during November-January:

Drivers:

Crop residue burning — 50-100 million tonnes of paddy stubble burnt in Punjab/Haryana every October.
Temperature inversions — cold ground + warmer aloft trap pollutants near surface.
Stagnant winds — calm pre-winter atmosphere prevents dispersal.
High humidity — water droplets adhere to pollution particles, accelerating aerosol formation.
Diwali fireworks — adds annual spike late Oct/early Nov.
Year-round emissions — industries, vehicles, biomass cooking.

Health impact:

2 million premature deaths per year in India attributed to outdoor air pollution (GBD).
Delhi residents lose 11 years of life expectancy compared to clean-air baseline.
Children’s lung development permanently impaired.
Heart attacks, stroke, lung cancer, COPD rates elevated.

Recent peak haze episodes:

Nov 2016 Delhi smog — PM2.5 above 1,000 μg/m³ at peaks (40× WHO limit)
Nov 2019 Lahore-Delhi smog — schools closed, flights diverted
Nov 2023 Delhi smog — AQI sustained above 450 for weeks

How to protect yourself from haze

When AQI exceeds 100 or PM2.5 > 35 μg/m³:

Limit outdoor exertion — exercise indoors instead
Wear N95/KN95 mask outdoors (cloth/surgical masks don’t filter PM2.5)
Run HEPA air purifier indoors — most effective intervention
Keep windows closed during peak haze hours
Vulnerable people (children, elderly, asthmatics, heart patients) stay indoors
Hydrate — supports respiratory clearance
Avoid traffic-heavy roads especially during morning/evening rush

For severe smog (AQI > 300):

Government may close schools and outdoor activities
Construction work may be halted (GRAP in Delhi)
Reduce vehicle use; use public transport

Policy and outlook

India’s National Clean Air Programme (NCAP) targets PM2.5 reduction in 131 non-attainment cities. Pakistan’s Punjab Smog Plan addresses cross-border pollution. Bangladesh participates in the Bangladesh Air Quality Management Project.

Tangible interventions:

Happy Seeders for crop-residue mulching instead of burning
Coal-to-gas conversion at Delhi power plants
BS-VI emission standards for vehicles since 2020
Mandatory FGD at thermal plants (lagging implementation)
GRAP Graded Response Action Plan in Delhi

Progress has been slow but measurable — Delhi’s average PM2.5 has dropped ~15% over a decade, though winter peaks remain dangerous.

Frequently asked questions

What’s the difference between haze and fog? Fog is water droplets (relative humidity ~100%, visibility < 1 km). Haze is dry particles (low humidity, dust/smoke/pollutants). Haze is much more harmful to health because it contains PM2.5 and PM10. Smog combines both.

Why is north India so much hazier than south India? North India’s plains topography (no escape route for pollutants), combined with cold winter temperature inversions, stagnant air, and intensive crop-residue burning, creates a perfect storm of trapped pollution. South India’s coastal location, sea breezes and warmer winters disperse pollution faster.

Is haze worse than it used to be? PM2.5 levels in Delhi peaked around 2016 and have declined slightly since due to NCAP, BS-VI emission norms and Diwali firework restrictions. But winter peaks remain among the highest in the world. Pakistan’s Punjab has seen rising trends due to industrial growth.

How does haze affect aviation? Visibility below 800 m forces airports to switch to instrument-only operations (CAT II/III). Delhi IGI Airport has CAT III-B capability allowing landings at 50 m visibility, but many smaller airports (Patna, Lucknow, Varanasi, Amritsar) without CAT III close completely. Pakistan’s Lahore similarly affected.

Where can I see live haze/AQI for my city? Mausam Online displays live PM2.5, PM10 and European AQI on every city page. See Delhi, Lahore, Patna, Kanpur, Dhaka, Faisalabad.