Air Quality Categories

Air quality was exceptionally good across the Namoi/North West Slopes region in spring 2025, remaining below national benchmarks 100% of the season (91 days).

The Namoi/North West Slopes recorded the following air quality categories (AQCs) for spring 2025:

• Below benchmarks:
  • Good AQC: 70 days (77% of spring days)
  • Fair AQC: 21 days (23%)

Exceedances

All pollutants in the region remained below their respective benchmarks in spring 2025.

Trends

Season

The Namoi/North West Slopes region experienced no days above national benchmarks in spring 2025 compared to 5 days in winter 2025. Average spring rainfall and very much above average temperatures may have reduced woodsmoke and opportunities for hazard reduction burning following more mild conditions in winter.

The 21 Fair AQC days during spring were mostly due to ozone at Tamworth and Gunnedah. In comparison, winter had 11 days in the Fair AQC, which were all due to PM2.5 particles. There was one day in spring (9 October) where all sites across the region recorded either Fair PM10 or PM2.5. This was likely caused by bushfire smoke originating from South East Queensland.

No exceedances were recorded in spring 2025, while 2 exceedances were recorded in spring 2024 and 1 in spring 2023. The number of days in the Fair AQC in spring 2025 were similar to spring 2024 and 2023. Ozone accounted for most Fair days in spring 2025 and 2023, however, approximately half the Fair days in spring 2023 were due to particulate matter, primarily from Wil-gai.

12-month review

The PM10 and PM2.5 particles 12-month rolling averages from 1 December 2024 to 31 November 2025 were below the annual benchmark levels at all stations. Levels at Tamworth, Gunnedah, Narrabri and Maules Creek were similar to previous 12-month periods. Werris Creek and Wil-gai recorded lower levels than the 1 December 2023 to 30 November 2024 period, where benchmarks were exceeded. The 1 December 2018 to 30 November 2019 period remains the highest recorded pollutant levels, where bushfires and dust storms significantly impacted air quality.

Ozone in the region from 1 December 2024 to 30 November 2025 followed similar trends to previous 12-month periods, with high levels in spring and summer and little to none in autumn and winter.