Worst Air Quality Months by City
Understanding when air quality is worst helps you plan activities, protect your health, and make informed decisions about travel and relocation. Each region has distinct pollution patterns driven by seasonal factors.
Worst Months by Major City
West Coast
Los Angeles
Daily Code Orange/Red alerts common. Heat + traffic + geography = persistent ozone problems.
Seattle / Portland
Smoke from regional fires can create hazardous conditions for weeks. September 2020 AQI exceeded 400.
San Francisco / Bay Area
Typically excellent air but wildfire smoke from mountains creates worst annual pollution events.
San Diego
Better than LA but still summer ozone concerns. Santa Ana winds bring inland pollution and fire smoke.
Mountain West
Salt Lake City / Provo
Worst air quality in nation during inversions. Can last 2+ weeks with AQI exceeding 150 daily.
Denver
Brown cloud visible during inversions. Less severe than Utah but still concerning for sensitive groups.
Phoenix
110°F+ temperatures drive severe ozone formation. Dust storms add particulate pollution.
Boise / Spokane
Regional wildfires create smoke that settles in valleys. Can persist for weeks in bad fire years.
Texas & Southwest
Houston
Petrochemical industry + heat + humidity = frequent ozone alerts. Among worst summer air in US.
Dallas-Fort Worth
Massive metro area with vehicle emissions. Summer heat creates persistent ozone exceedances.
Austin / San Antonio
Texas Hill Country offers some relief but summer heat still drives ozone formation. Better than Houston.
Las Vegas
Desert heat drives ozone. Dust from development. California wildfire smoke can reach valley.
Northeast & Mid-Atlantic
New York City
Heat waves create ozone alerts. Canadian wildfire smoke events (June 2023 hazardous levels).
Philadelphia / Baltimore
I-95 corridor pollution. Summer heat and humidity create frequent Code Orange days.
Washington DC
Swampy summer conditions perfect for ozone formation. Heat index often exceeds 100°F.
Boston
Coastal location provides some relief but still sees summer ozone alerts during heat waves.
Midwest & Great Lakes
Chicago
Lake Michigan moderates but summer still brings ozone days. Canadian wildfire smoke impacts possible.
Detroit / Cleveland
Much improved from industrial past. Summer heat still creates ozone alerts during stagnant conditions.
Minneapolis
Generally excellent air but vulnerable to Canadian wildfire smoke. Heat waves can create local ozone.
St. Louis
Mississippi River humidity combined with summer heat creates ozone formation conditions.
Southeast
Atlanta
City in a forest. Trees emit VOCs + heat + vehicle emissions = summer ozone alerts.
Miami / Tampa
Generally better than inland cities. Ocean breezes help. Occasional Saharan dust plumes add particulates.
Charlotte / Raleigh
Piedmont location with summer humidity. Moderate ozone issues during peak heat.
New Orleans
Extreme humidity + heat + petrochemical industry. River location adds stagnation during summer.
Protection During Worst Months
Daily Monitoring
- • Check AQI forecast every morning
- • Set up air quality alerts on phone
- • Follow local air quality agencies
- • Monitor weather forecasts for heat waves
- • Track wildfire activity in your region
Activity Adjustments
- • Move exercise indoors on bad days
- • Schedule outdoor activities for mornings
- • Avoid peak afternoon ozone hours (2-6pm)
- • Reduce time near busy roads
- • Have indoor backup plans ready
Indoor Air Quality
- • Run HEPA air purifiers continuously
- • Keep windows closed during pollution events
- • Use HVAC on recirculate mode
- • Consider portable AC for cleaner indoor air
- • Upgrade to MERV 13+ filters