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.