Air Quality Categories

Air quality was exceptionally good across the Upper Hunter region in winter 2025. Levels remained below national benchmarks over 97% of the season (89 days), helped by above average rainfall during the season.

The Upper Hunter recorded the following air quality categories (AQCs) for winter 2025:

• Below benchmarks:
  • Good AQC: 79 days (86% of winter days)
  • Fair AQC: 10 days (11%)
• Above benchmarks:
  • Poor AQC: 3 days (3%)

Exceedances

National benchmarks were exceeded on 3 days during winter 2025, all due to PM10 particles. These occurred on 10 July at Warkworth and Camberwell, 20 July at Mount Thorley, and on 8 August at Warkworth. These exceedances were likely influenced by industrial or mining activity.

PM2.5 particles, nitrogen dioxide, sulfur dioxide and ozone remained below national benchmarks during winter 2025.

Trends

Season

Overall, regional air quality in winter 2025 was similar to autumn 2025. Winter recorded 3 exceedance days compared to the 4 days recorded during autumn. The continued good air quality has been helped by above average rainfall during winter, following on from very much above average rainfall during autumn.

Winter 2025 was similar to both winter 2024 and 2023, both of which recorded 4 days each over benchmarks. Winter 2025 was wetter and much cooler than both these winters.

12-month review

The 12-month rolling averages from 1 September 2024 to 31 August 2025 for PM10 and PM2.5 particles were generally below annual benchmark levels. Warkworth (28.5 µg/m3) exceeded annual benchmark levels during the 12 months to the end of winter 2025, likely due to mining activity in the area. Warkworth has consistently recorded the region’s highest PM10 annual averages in recent years. Rolling annual average levels were slightly lower at most stations compared to the same period the previous year. 12-month rolling PM10 concentrations at most stations have returned to levels observed before the 2019-2020 bushfire season, while PM2.5 levels remain stable at lower concentrations.

Very-much-above-average rainfall was observed during the 12 months to the end of August 2025, much of which occurred during autumn and winter. This likely contributed to low particle concentrations.