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.

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.

Air Quality Categories

Air quality was generally fair in the Upper Hunter during spring 2025. Levels remained below national benchmarks on 71 days (77.2% of the season).

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

• Below benchmarks:
  • Good AQC: 30 days (32.6% of spring days)
  • Fair AQC: 41 days (44.6%)
• Above benchmarks:
  • Poor AQC: 19 days (20.7%)
  • Very Poor AQC: 2 day (2.2%)

Exceedances

Twelve of 14 stations exceeded the PM10 daily benchmark on 21 days during spring 2025. Two days reached the Very Poor AQC, the other 19 days reached the Poor AQC. Twenty of these exceedance days were due to local dust, likely associated with nearby mining activity. One day (14 November) exceeded due to bushfire smoke as well as dust.

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

Trends

Season

National benchmarks were exceeded on 21 days in spring 2025, compared to 3 days during winter. Of those 21 exceedance days, 13 occurred at individual stations only, with Warkworth accounting for 8 days.

The significant increase in days above benchmarks is likely a regular seasonal shift, owing to warmer weather drying out exposed soil due to mining activity, increasing the chance of windblown dust. The Upper Hunter experienced highest on record daily maximum temperatures and below average rainfall during spring, compared to a much cooler (average temperatures) and wetter winter. This shift in conditions also likely explains the higher proportion of Fair AQC days in spring (41 days) compared to winter (10 days). Warkworth recorded Fair AQC on 31 of the 41 Fair AQC days in spring.

Spring 2025 recorded a similar number of exceedances compared to spring 2024 (15 days) and spring 2023 (23 days), and as with recent years, benchmark exceedances were driven by sites close to mines. Warkworth recorded the highest number of exceedances (13 days) in the region during spring, a trend that began in 2023. Spring 2025 was relatively hotter and drier than the two previous spring seasons.

12-month review

12-month PM10 and PM2.5 averages to the end of November 2025 were below national benchmarks at all stations except Warkworth (PM10; 29.2 µg/m3). Averages were generally similar to those to the end of November 2024. 12-month averages for PM10 at most stations have returned to similar levels as those observed before the 2019-2020 bushfire season, while PM2.5 averages remain stable below those levels. Warkworth recorded its third-highest 12-month PM10 average since the network began, with two of the three highest averages occurring after the 2019-2020 bushfire season.

Higher than average rainfall during autumn and winter 2025 likely limited airborne dust particles. Highest on record maximum temperatures during spring likely drove a region-wide increase in PM10, leading to 12-month PM10 averages similar to the previous period (December 2023 to November 2024). This is despite lower rainfall during the December 2023 to November 2024 period.