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Šiauliai, the fourth-largest city in Lithuania, occupies a central position within the Šiaulių Miestas municipality. Its geography is defined by the North Lithuanian Plain, a gently undulating landscape sculpted by glacial activity during the last ice age. The city sits approximately 130 meters above sea level, a relatively flat elevation contributing to potential temperature inversions. The Šiaulė river, a tributary of the Nemunas, flows through the city, but its influence on widespread air dispersion is limited due to its moderate size and flow rate. Historically, Šiauliai developed as a trade and industrial hub, and remnants of this industrial past – including manufacturing and processing facilities – are located both within and on the periphery of the urban area. Surrounding the city is a predominantly agricultural landscape, characterized by arable land and scattered forests. This agricultural zone contributes to seasonal particulate matter pollution from farming activities. The urban-rural gradient is relatively sharp, with a noticeable increase in population density and traffic volume as one approaches the city centre. This concentration of sources, coupled with the flat terrain, can exacerbate localised air pollution episodes. The prevailing winds, generally from the west, play a crucial role in pollutant transport and dispersion, but can also carry pollutants from regional sources.

Šiauliai experiences a temperate continental climate, resulting in distinct seasonal air quality patterns. Winter (December-February) often sees the poorest air quality, driven by increased reliance on solid fuel heating for residential purposes, coupled with stable atmospheric conditions and frequent temperature inversions trapping pollutants near the ground. Fog, common during these months, further reduces dispersion. Spring (March-May) brings a gradual improvement as temperatures rise and heating demand decreases, though agricultural activities begin to contribute to particulate matter. Summer (June-August) typically offers the cleanest air, benefiting from prevailing winds and reduced heating needs. However, occasional heatwaves can lead to increased ground-level ozone formation. Autumn (September-November) sees a deterioration as heating systems are reactivated and damp conditions can exacerbate particulate pollution. Sensitive individuals – children, the elderly, and those with respiratory conditions – should be particularly cautious during the winter months and periods of stagnant air. Avoiding strenuous outdoor activity during peak pollution times, and monitoring local reports, is advisable. The months of June through August generally present the most favourable conditions for outdoor recreation. Wind direction shifts can also bring in pollutants from surrounding regions, impacting local air quality.