The ACT’s grass pollen season occurs each year when grasses in rainfed pastures around Canberra begin to flower and release pollen into the air. It typically runs from October through December and is a major trigger of respiratory allergies such as hay fever and asthma. Seasonal forecasts are intended as an aid to help people prepare, as both the timing and severity of the season are strongly influenced by climate conditions, particularly rainfall.

Setting the Scene: How 2024 Played Out

In 2024, low soil moisture across the southern tablelands meant Canberra experienced a mild season, with just 4 high and 23 moderate grass pollen days between October and December. The remaining 65 days were in the low range, and by early December the season had effectively ended. This year, conditions are shaping up differently. A wet July has left soils in much better condition than at the same time last year, providing a stronger foundation for grass growth this spring.

Soil Moisture Conditions

Rainfall across the ACT in 2025 has been about average, and root-zone soil moisture, an important indicator of water available for grass growth and flowering, is generally close to average across the region. Figure 1 shows that while some areas west of Canberra are drier, overall soils are far wetter than they were in August 2024.

Figure 1: Relative root zone soil moisture levels for south-eastern Australia for August 2025 and August 2024 for comparison. Images are modified from https://awo.bom.gov.au.

Vegetation Greenness and Growth Potential

Grasses in the southern tablelands follow a familiar temperate climate cycle: winter dormancy, rapid growth and flowering in spring, and drying off in summer. Satellite imagery allows us to track these changes. As shown in Figure 2, the countryside surrounding Canberra appears noticeably greener this August compared with last year. This is especially true to the north and indicates more vigorous grass growth heading into spring.

Figure 2: Satellite-based imagery of vegetation greenness for south-eastern Australia for August 2025 and August 2024 for comparison.

Climate Drivers and the Rainfall Outlook

Looking ahead, climate models point to a negative Indian Ocean Dipole or -IOD, a key driver often linked to wetter conditions in south-eastern Australia. For the ACT, this means an increased likelihood of above-average rainfall and warmer daytime temperatures during spring 2025. The Bureau of Meteorology outlook (Figure 3) shows a 65–70% chance of above-median rainfall between October and December this year.

While above-median rainfall can only mean a few millimeters more than usual, Figure 3 shows there are signs that this spring could be particularly wet in Canberra. The Bureau of Meteorology is forecasting more than double the usual chance of an unusually wet spring, especially in October. An unusually wet spring is one where the rainfall is in the top 20 per cent of all years.

Figure 3: Chance of south-eastern Australia exceeding the median rainfall for October to December 2025 (left). Chance of rainfall in the highest 20 per cent of the historical range for September to November (right). Images modified from the Bureau of Meteorology.

What This Means for the Season Ahead

At present, the outlook suggests a season close to the 5-year average, which means we can expect around 20 high or extreme grass pollen days expected between October and December. These are the days that most severely affect people with hay fever and asthma. However, conditions in September and October will be crucial. If these months are wet, the combination of moisture, warmer weather, and longer days could fuel vigorous grass growth, leading to a much heavier season. If not, pollen levels may remain closer to average.

How to Prepare

With the potential for a wetter spring and a heavier pollen season, preparation is essential. People with hay fever or asthma should speak to their doctor or pharmacist before the season begins to review treatment plans. Those with asthma are strongly encouraged to have a written Asthma Action Plan in place so they know exactly what steps to take if symptoms worsen.

For more information about pollen levels and your health visit the ACT Government visit: https://www.act.gov.au/environment/air-quality/pollen-levels-and-your-health

The best way to stay informed about how much pollen is in our shared air is to visit the Canberra Pollen website or download the Canberra Pollen App on the Apple App or Google Play store, where you’ll find daily pollen forecasts, push notifications, and tips to help manage your exposure. You can also follow Canberra Pollen on social media on X (formally Twitter) and Facebook for updates throughout the season.

The Bottom Line

The 2025 ACT grass pollen season is expected to be more active than last year, though the final outcome depends heavily on rainfall in early spring. Wet conditions could drive stronger grass growth and higher pollen levels, while drier weather may keep the season closer to average. Either way, staying prepared and keeping up to date with daily forecasts will help reduce the impact on your health.