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Nestled in southeastern Louisiana along the Mississippi River, New Orleans occupies a unique geographic position that profoundly influences its air quality. Situated approximately 105 miles upriver from the Gulf of Mexico, the city lies within the Mississippi River Delta, characterized by flat, low-lying terrain with an average elevation of just 1 to 2 feet below sea level in many areas, creating a bowl-like topography. This urban center is surrounded by extensive wetlands, bayous, and Lake Pontchartrain to the north, which moderates temperatures but also traps pollutants. The city's location places it within the industrial corridor known as 'Cancer Alley,' stretching along the Mississippi River from Baton Rouge to New Orleans, where numerous petrochemical plants, refineries, and shipping facilities contribute significantly to regional air pollution. The urban-rural gradient shows dense urban cores giving way to suburban sprawl and then to agricultural zones growing sugarcane and soybeans, with prevailing southerly winds often carrying industrial emissions into the metropolitan area. New Orleans' position at the mouth of the Mississippi River basin means it receives air masses that have traveled over agricultural regions with pesticide applications and industrial zones, while its coastal location brings marine air that can dilute pollutants but also contributes to high humidity that facilitates secondary pollutant formation.

New Orleans experiences distinct seasonal air quality patterns shaped by its humid subtropical climate. During winter (December-February), cooler temperatures and frequent cold fronts bring cleaner air from the north, though temperature inversions can occasionally trap pollutants near the ground, particularly during calm mornings. Spring (March-May) sees increasing temperatures and humidity, with pollen from abundant vegetation becoming a significant concern, peaking in April; this season also brings occasional prescribed agricultural burns upriver. Summer (June-August) presents the most challenging air quality conditions, with intense heat, high humidity, and stagnant air masses creating ideal conditions for ozone formation, particularly during afternoon hours when sunlight interacts with vehicle emissions and industrial pollutants; July and August typically show the highest pollution levels. Autumn (September-November) begins with residual summer conditions but improves as cooler, drier air arrives, though hurricane season can stir up dust and mold spores. Sensitive groups should limit prolonged outdoor exertion during summer afternoons and spring pollen peaks, while winter generally offers the cleanest air for outdoor activities. The city's coastal breezes provide some relief, but industrial emissions from upriver facilities can affect air quality during periods of northerly winds.