Air Quality Categories

Air quality was exceptionally good across the Upper Hunter region in autumn 2025. Levels remained below national benchmarks over 96% of the season (88 days), driven largely by wet conditions, with very much above average rainfall for the season.

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

• Below benchmarks:
  • Good AQC: 70 days (76% of autumn days)
  • Fair AQC: 18 days (20%)
• Above benchmarks:
  • Poor AQC: 3 days (3%)
  • Very Poor AQC: 1 day (1%)

Exceedances

National benchmarks were exceeded on 4 days during autumn 2025, all due to PM10 particles.

A dust storm originating in South Australia and Victoria passed over eastern New South Wales on 27 May. Across the network, 60% of monitoring stations exceeded the national benchmark (Very Poor and Poor AQC) due to this dust storm, including all 14 Upper Hunter stations.

Aside from the dust storm, daily PM10 exceedances occurred at Warkworth (2 days) and Mount Thorley (1 day), with the 2 stations likely impacted by nearby mining activities.

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

Trends

Season

Autumn 2025 recorded 4 exceedance days, similar to summer 2024-25 (6 days), where exceedances were also only recorded at Jerrys Plains (1 day) and Warkworth (5 days).

Eighteen days with Fair AQC were recorded in autumn 2025, compared to 30 days during summer 2024-25. The highest number of Fair AQC days was recorded at Warkworth during both seasons, likely resulting from mining activity. This decrease is likely due to the very much above average rainfall recorded across the Upper Hunter during autumn, compared to generally average during summer 2024-25.

Autumn 2025 was similar to autumn 2024 (2 days above PM10 benchmarks). Air quality during autumn 2025 was improved compared to autumn 2023 (9 days above benchmarks; 8 from PM10, one from sulfur dioxide). Autumn 2025 was wetter than both autumn 2024 and 2023.

12-month review

The PM10 and PM2.5 12-month rolling averages from 1 June 2024 to 31 May 2025 were below the annual benchmark levels at all stations, except for PM10 at Warkworth (28.4 µg/m3). Rolling annual average levels fell at most stations compared to the same period the previous year, likely due to wetter conditions with above average rainfall to the end of autumn 2025. PM10 levels continue to show a recovery from those recorded during the La Nina years from 2020 to 2023, while PM2.5 levels were at or near the record low concentrations recorded during the June to May periods in 2021-2022 and 2022-2023.

Warkworth has consistently recorded the region’s highest PM10 annual averages in recent years, likely due to nearby mining activities.