Air Quality Categories

Air quality was exceptionally good across the Namoi/North West Slopes region in winter 2025, remaining below national benchmarks on 87 days (95%).

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

• Below benchmarks:
  • Good AQC: 76 days (83% of winter days)
  • Fair AQC: 11 days (12%)
• Above benchmarks:
  • Poor AQC: 5 days (5%)

Exceedances

National benchmarks were exceeded on 5 days during winter 2025, all due to PM2.5 particles from woodsmoke and all at Gunnedah.

PM10, ozone, and nitrogen dioxide all remained below their respective benchmarks for the season.

Trends

Season

In winter 2025, the Namoi/North West Slopes region experienced 5 days above national benchmarks compared to 1 day in autumn 2025. The 5 winter exceedances all being due to PM2.5 point to smoke from domestic wood heaters as a likely source. This also likely explains the increase in Fair AQC days during winter (11 days) compared to autumn (5 days).

Days above the PM2.5 benchmark in winter due to woodsmoke are a regular occurrence at Gunnedah in particular, with one exceedance day each occurring during winter 2024 and 2023. Days in the Fair AQC were similar between winter 2025 and 2024, with 11 days compared to 13 days, respectively, with 18 days in 2023.

Regional rainfall was average to very-much-above average during winter.

12-month review

The PM10 and PM2.5 particles 12-month rolling averages from 1 September 2024 to 31 August 2025 were below the annual benchmark levels at all stations. Levels at Gunnedah, Tamworth, Narrabri and Maules Creek were similar to previous 12-month periods, and were slightly lower than the 1 September 2023 to 31 August 2024 period. Werris Creek and Wil-gai recorded their second-highest levels since the network was established. However, these were much lower than the 1 September 2019 – 31 August 2020 period, during which air quality was significantly impacted by bushfires and dust storms.