The Air Quality Index, or AQI, turns the pollution in the air into one simple number. Instead of reading a list of chemical measurements, you read one number and you know immediately whether the air is safe to breathe. This page shows the live AQI for cities around the world, powered by OpenAQ air quality stations, alongside the weather. If the air quality matters to you — and in winter in Pakistan, it should — this guide explains what the AQI number means, what causes bad air, and what you can do about it.
The AQI scale runs from 0 to 500. A number from 0 to 50 means good air: clean and safe for everyone, and normal outdoor activity is fine. From 51 to 100 the air is moderate: acceptable for most people, though very sensitive people should watch for symptoms. From 101 to 150 the air is unhealthy for sensitive groups: children, older people, and anyone with asthma or heart problems should reduce their time outside. From 151 to 200 the air is unhealthy for everyone, and long outdoor exercise should be avoided. From 201 to 300 the air is very unhealthy: stay indoors as much as possible and wear a mask outside. Above 300 the air is hazardous, and going outside should be avoided unless necessary.
What Is PM2.5 and Why Does It Matter?
The most important pollutant in the AQI is PM2.5: tiny particles less than 2.5 micrometres wide, about thirty times thinner than a human hair. They come from vehicle exhaust, smoke from burning, brick kilns, factories and dust. Because they are so small, they go deep into the lungs and even into the blood, which is why PM2.5 is linked to coughing, asthma attacks, and long-term breathing and heart problems. A second pollutant, PM10, is made of larger dust particles that irritate the eyes, nose and throat. When the AQI is high, PM2.5 is usually the reason.
Smog is what happens when PM2.5 and other pollutants mix with damp winter air and get trapped close to the ground. In Lahore and other cities in Punjab, smog season runs from late October to January, with November and December the worst months. Crop residue burning, traffic exhaust, brick kilns and construction dust all add pollution at the same time, and cold, still winter air traps it over the city. Our smog in Lahore guide explains the causes in detail, including smog holidays and smog lockdowns, and how to stay safe during the worst days.
How to Check the Air Quality in Your City
Check the AQI in the morning before leaving home, because the air is usually worst early in the day and improves a little by the afternoon. On this page, pick your city and read the AQI number first, then the PM2.5 reading if it is available. If the AQI is above 100, sensitive people should stay indoors. If it is above 150, everyone should avoid long outdoor exercise. If it is above 200, wear a proper N95 mask outside — a simple cloth mask does very little against fine particles — and keep windows closed at home.
Air quality changes through the day and through the year. It is worst on cold, still mornings and best on windy days and after rain, because wind blows the pollution away and rain washes it out of the air. Summer usually has better air than winter in Pakistan, because the air is warmer and moves more. But dust storms in summer can also push the AQI up for a day or two. The weather and the air quality are connected: check both before you plan your day. Every city page on Weather Tomorrow shows the weather and the air quality together.
How to Stay Safe When the Air Is Bad
You cannot control the air, but you can reduce how much pollution you breathe. Stay indoors in the morning when the smog is thickest, and delay outdoor work until the afternoon if you can. Avoid running or playing outside when the AQI is above 150, because exercise makes you breathe much more polluted air. Keep windows and doors closed on heavy smog days and use an air purifier indoors if you have one. Drink water, watch for symptoms like burning eyes, a sore throat or constant coughing, and keep your inhaler close if you have asthma. Children and older people need the most protection, because their lungs are the most sensitive to bad air. Check the air quality every morning during the winter season, just like you check the weather, and plan your day around both numbers together.
