Exeter Air Quality Index (AQI)

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Exeter, New Hampshire, nestled in the Piscataqua River watershed, presents a unique geographic context influencing its air quality. Situated in Rockingham County, the town occupies a relatively low-lying area, averaging around 60 feet in elevation, though the surrounding terrain rises quickly towards the western foothills of the White Mountains. This proximity to both coastal plains and higher ground creates localized weather patterns that impact pollutant dispersion. The town’s location, approximately 12 miles inland from the Atlantic Ocean at Portsmouth, moderates temperatures but also introduces the potential for marine air masses carrying pollutants. Historically, Exeter developed as a mill town, leveraging the power of the Exeter River, a tributary of the Piscataqua. While large-scale industry has diminished, residual impacts from past activities and the presence of smaller businesses contribute to localized emissions. The surrounding landscape is a mix of deciduous forests, agricultural land – particularly to the west – and increasingly, suburban development. This urban-rural gradient means Exeter experiences a blend of rural background pollution and emissions from transportation and residential heating. The relatively flat terrain can sometimes exacerbate temperature inversions, trapping pollutants near the ground, particularly during calm weather conditions. The town’s position within the Boston-Washington corridor also means it’s subject to long-range transport of pollutants from more heavily industrialized areas.

Exeter’s air quality follows a distinct seasonal pattern. Spring (March-May) often sees a rise in particulate matter from agricultural activities and road salt residue, coupled with pollen. Winds begin to pick up, aiding dispersion, but temperature inversions can still occur, trapping pollutants. Summer (June-August) generally offers the cleanest air, with prevailing southwesterly winds flushing out pollutants and higher temperatures promoting atmospheric mixing. However, ozone formation can be a concern on hot, stagnant days, particularly downwind of traffic corridors. Autumn (September-November) brings vibrant foliage but also increased wood smoke from residential heating, contributing to particulate matter pollution. This is often exacerbated by stable atmospheric conditions as the jet stream shifts. Winter (December-February) is typically the period of poorest air quality. Cold temperatures drive increased use of fossil fuels for heating, leading to higher concentrations of sulfur dioxide, nitrogen oxides, and particulate matter. Snow cover reflects sunlight, intensifying temperature inversions and trapping pollutants close to the ground. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit strenuous outdoor activity during prolonged cold snaps and periods of wood smoke. Monitoring wind patterns and avoiding peak heating hours can help mitigate exposure.