Air Quality Index: The Ultimate Weather Sensitivity Guide

Fact checked by Olga Sadouskaya, MD
Clinical Pharmacologist, Chief Medical Officer

Air quality is an important issue that a lot of people don’t know enough about. Air pollution is responsible for around 7 million deaths each year. That’s more than the deaths caused by AIDS, tuberculosis, and malaria combined.

Continue reading to find out how the air quality index is calculated, the meaning behind different AQI levels, and the health effects of air pollution.

What is the air quality index?

The air quality index, or AQI, is a measure of the quality of the air we breathe. It provides a snapshot of the levels of harmful pollutants in the air and assigns them a numerical value, making it easy for people to understand the air quality in their area.

The AQI is a critical tool for monitoring and managing air quality, as it helps people understand the impact of air pollution on their health and the environment.

By providing real-time information about air quality, the AQI can help people make informed decisions about activities such as outdoor exercise and travel.

Additionally, the AQI helps policymakers, scientists, and communities to take action to reduce air pollution and improve air quality.

AQI forecast: How is the air quality index calculated?

The AQI is an index for reporting daily air quality. The AQI in the United States was developed by the Environmental Protection Agency in 1999 and provides information on how clean or polluted local outdoor air is.

The AQI measures five major air pollutants:

  • Ground-level ozone
  • Particle pollution (also known as particulate matter)
  • Carbon monoxide
  • Sulfur dioxide
  • Nitrogen dioxide
A man wearing a mask on a busy street to negate the health effects of air pollution

The calculation of the AQI considers all five pollutants and then assigns a number from 0 to 500 based on how severe each pollutant’s level is at a given location. The higher the index value, the more hazardous the air quality is.

Data collected from monitoring stations located throughout various cities is used to calculate the AQI forecast for that particular city or region. The data includes measurements of temperature, pressure, wind speed, and direction, as well as levels of various pollutants, such as ozone, particulate matter, carbon monoxide, and nitrogen dioxide.

This data is then combined with other factors, such as population density and geographic features like mountains or valleys, which can affect air circulation patterns and further impact local pollution levels. The people in that area can use the resulting AQI forecast to plan their outdoor activities accordingly so they can minimize their exposure to potentially dangerous levels of pollutants in the environment.

How does the weather affect air quality?

The weather can have a major effect on air quality. Everything from temperature to wind speed and precipitation can change the way pollution levels fluctuate throughout the day. And understanding this relationship is key to managing air quality in our environment. So let’s take a look into how the weather affects air quality.


Temperature is one of the most important factors to consider when looking at air quality. Generally speaking, higher temperatures can increase ground-level ozone levels by increasing the chemical reactions that create it.

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In the summer months, this can lead to intense smog episodes and poor air quality in urban areas. On the other hand, colder temperatures help reduce ground-level ozone levels because they slow down the chemical reactions that create it. This means that places with colder winters tend to have better overall air quality than places with warmer winters.

Wind and precipitation

Wind and precipitation are also important factors to consider when looking at air quality. Wind helps disperse pollutants like dust and smoke, which reduces ground-level ozone concentrations in heavily polluted areas like cities.

But strong winds can also be damaging by carrying pollutants from one area to another, leading to poor air quality in otherwise clean environments, such as rural areas or national parks.

Precipitation also helps remove some pollutants from the atmosphere, but only if it’s heavy enough. Light rain isn’t enough for particles like dust and smoke to actually fall out of the sky, so they remain suspended until heavier rain comes along or wind disperses them elsewhere.

AQI scale: Different levels of the air quality index

The AQI in the United States is divided into six categories that represent different levels of health concern associated with each pollutant or pollutant group:

  • Good (0–50)
  • Moderate (51–100)
  • Unhealthy for sensitive groups (101–150)
  • Unhealthy (151–200)
  • Very unhealthy (201–300)
  • Hazardous (301–500)

Each level has its own color associated with it and includes specific recommendations for reducing your exposure based on the level of health concern and type of pollutant present in your area.


When AQI values are in this range, air quality is considered satisfactory, and there are no health concerns associated with it. This means that everyone can safely enjoy outdoor activities without worrying about adverse health effects from breathing polluted air.

A couple cycling in a park when the air quality index is good


In these conditions, some people may begin to experience minor reactions, such as coughing or sneezing, due to exposure to airborne particles or ozone.

People with asthma, allergies, or other respiratory illnesses should take special precautions when spending time outdoors because they may be more sensitive than others when exposed to elevated levels of pollutants in the air.

Unhealthy for sensitive groups

These conditions can cause serious respiratory problems like chest tightness and shortness of breath in sensitive individuals, such as those with asthma, allergies, chronic bronchitis, emphysema, or heart disease.

Everyone should limit their time outdoors during these conditions unless absolutely necessary.

Unhealthy, very unhealthy, and hazardous

At these levels of pollution, even healthy individuals may begin experiencing symptoms, such as difficulty breathing or eye irritation, due to exposure to high concentrations of pollutants in the air.

Everyone should avoid outdoor activities altogether, if possible, during these times, as long-term exposure can lead to more severe health problems such as cancer or organ damage over time.

Health effects of air pollution

Air pollution’s health effects are a major issue for millions of people around the world. Polluted air can cause a variety of health problems, ranging from respiratory issues to cardiovascular diseases.

Air pollution can have severe short-term effects on human health. These include difficulty breathing, headaches, fatigue, coughing, and an increased risk of asthma attacks.

Long-term exposure to polluted air can lead to more serious health issues, such as chronic bronchitis and even cancer.

Studies have also linked air pollution to an increased risk of heart attack and stroke due to the hardening of the arteries and inflammation in the lungs.

The long-term effects of air pollution are just as concerning as the short-term effects. Prolonged exposure to polluted air has been linked to an increased risk of developing diseases such as lung cancer, chronic obstructive pulmonary disease, and other respiratory illnesses.

Studies have also found a correlation between air pollution and dementia due to damage caused by pollutants entering the brain through inhalation or from particles entering through wounds in the skin.

Air pollution has also been linked to a higher risk of sleep disorders like sleep apnea and reduced sleep quality and duration.

What to do when the air quality is bad

Air quality can have a significant impact on our health and well-being. There are times when air pollution levels become so high that staying indoors is the only way to protect ourselves. But what else can we do when the air quality outside is bad? Let’s explore some of the ways we can stay safe during periods of poor air quality.

1. Monitor local air quality levels

The best way to stay informed about local air quality levels is to follow your local news or check an online resource like the Environmental Protection Agency’s AirNow website, which provides real-time updates on current air quality conditions across the United States.

If you know that air pollution levels are high in your area, it’s best to limit outdoor activities until those levels go down.

2. Practice healthy habits indoors

When you’re stuck inside due to poor air quality, make sure you practice healthy habits, like keeping windows and doors closed at all times and running an air purifier with HEPA filters and an AQI monitor.

Make sure that you’re getting plenty of rest and drinking enough water as well. These habits will help keep your immune system strong enough to fight off any pollutants that may be present in the home.

Download WeatherWell to stay informed about the air quality in your area and get personalized tips to stay protected no matter the conditions!

3. Prepare ahead of time for future poor air quality events

It’s important to be prepared for future events when poor air quality may be an issue. Keep a stockpile of essential items like face masks and hand sanitizer on hand just in case the need arises again.

You should also familiarize yourself with any government regulations regarding indoor activities during periods of poor air quality. For example, some states may impose restrictions on certain types of business activities during these events.

By being aware of potential restrictions ahead of time, you can plan accordingly in order to ensure maximum safety for yourself and others around you.

Bottom line

Taking steps to protect yourself from poor air quality is essential in order to maintain good health and well-being during these times. Start by monitoring local air pollution levels and limiting outdoor activities when necessary. Moreover, you can also check the air quality index

March 21, 2023