On August 2, 2026, the air quality in Basel was characterized by elevated ozone levels, while nitrogen dioxide and particulate matter remained well within typical ranges. The maximum ozone concentration reached 144.7 µg/m³, exceeding the regulatory threshold of 120 µg/m³. This value ranked as the 22nd highest daily maximum in the past 365 days. The daily average ozone concentration was 99.8 µg/m³. In contrast, nitrogen dioxide peaked at 13.3 µg/m³, far below its 80 µg/m³ daily average limit, with an average of 7.2 µg/m³. Particulate matter (PM10) reached a maximum of 19.1 µg/m³ and averaged 14.1 µg/m³, both comfortably under the 50 µg/m³ daily average threshold.

Compared to the last 30 days, the maximum ozone reading was below the period’s peak of 175.3 µg/m³, and the average was slightly higher than the 30-day average of 97.0 µg/m³. For the current season, the day’s maximum ozone was also below the seasonal high of 175.8 µg/m³, while the average exceeded the seasonal average of 88.1 µg/m³. Nitrogen dioxide and PM10 values were unremarkable, with both maximums and averages closely aligning with recent 30-day and seasonal norms.

Looking at the historical record since 2018, the ozone maximum of 144.7 µg/m³ was not extreme. It ranked 132nd out of 2981 days, placing it well within the upper range but far from the all-time high of 206.3 µg/m³ recorded on June 27, 2019. Nitrogen dioxide and PM10 maximums were unexceptional historically, ranking 2501st and 1314th respectively. The absolute maximum NO₂ value of 83.2 µg/m³ occurred on February 15, 2019, and the highest PM10 reading of 165.1 µg/m³ was measured on August 24, 2023.

Overall, the air quality on this day was largely consistent with historical summer patterns, with the notable exception of ozone. The exceedance of the ozone threshold, while not unprecedented, indicates a day with considerable photochemical smog formation, likely driven by strong sunlight and precursor emissions. All other pollutants remained at low, unremarkable levels.