Alton Air Quality Index (AQI)

Loading live AQI data...

Loading historical AQI trends...

Alton, Illinois, nestled along the Mississippi River in the southwestern part of the state, occupies a unique geographic position that significantly influences its air quality. The city’s terrain is characterized by rolling hills and bluffs, a consequence of the river’s erosional power and the underlying geology of the Illinois Basin. Its elevation varies, reaching a modest peak of around 630 feet above sea level, creating localized microclimates and influencing air circulation patterns. The Mississippi River itself acts as a major geographical feature, moderating temperatures and contributing to humidity, but also potentially trapping pollutants under certain meteorological conditions. Alton sits within a transitional zone between the agricultural heartland of Illinois and the industrial belt of the Midwest. Extensive farmland surrounds the city, contributing to seasonal agricultural emissions, particularly during planting and harvesting periods. To the east lies the broader St. Louis metropolitan area, a significant source of regional air pollution. The urban–rural gradient is relatively sharp, with agricultural fields quickly giving way to suburban development and then to the urban core of Alton. The city’s location within the Mississippi River Valley can also lead to stagnant air conditions, especially during periods of high pressure, hindering pollutant dispersal. The surrounding landscape, a mix of forests, fields, and urban development, further complicates air quality dynamics, creating a complex interplay of sources and transport pathways.

Alton’s air quality experiences a distinct seasonal cycle driven by meteorological factors. Spring, from March to May, often sees elevated particulate matter levels due to agricultural activities like tilling and fertilizer application, combined with increased pollen counts. Wind patterns are variable during this period, sometimes aiding dispersion, but frequently leading to localized stagnation. Summer (June-August) typically brings higher temperatures and humidity, which can exacerbate ozone formation, although afternoon thunderstorms often provide temporary relief by flushing out pollutants. Fall (September-November) is arguably the most challenging season. Cooler temperatures combined with stable atmospheric conditions frequently lead to temperature inversions, trapping pollutants near the ground. Agricultural burning, though regulated, can also contribute to particulate matter. Winter (December-February) often presents the worst air quality, with cold, stable air and frequent fog events. These conditions inhibit vertical mixing and trap emissions from heating systems and vehicle exhaust. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should limit prolonged outdoor exertion during these periods, particularly on days with visible haze or fog. While summer thunderstorms can offer respite, the overall trend suggests minimizing outdoor activity during the fall and winter months, and being mindful of agricultural emissions in the spring. Careful monitoring of local weather forecasts and air quality reports is crucial for informed decision-making.