Indicator assessment
CONDITION

TREND

DATA QUALITY

Although fire severity risk conditions are highly variable in the ACT, periods of high risk occur regularly, potentially leading to more severe fires and greater difficulty in fire suppression. The fire severity risk conditions were particularly elevated in the month leading up to the Orroral Valley fire in 2020, as well as for the first two days of the fire. There has also been an increasing occurrence of consecutive fire seasons with elevated fire severity risk in the ACT.
Climate change is expected to further increase the ACT’s fire severity risk in the future.
Introduction
This indicator is assessed using the Fire Danger Index and the Fire Danger Ratings which are derived from the index. It should be noted that the Fire Danger Index and associated Fire Danger Ratings do not necessarily correspond to the incidence of bushfires, they only estimate the potential severity of bushfire occurrence given the predicted weather conditions. For more information see Background: Fire.
Fire Danger Rating System
Australia’s Fire Danger Rating System was updated in September 2022. The new rating system uses weather, fuel loads and fire behaviour in different vegetation types to assess fire severity danger. This differs greatly from the previously used Fire Danger Index which is calculated on weather indices alone. However, for consistency with previously reported data, and to enable a longer-term assessment of fire risk, this report does not use the updated Fire Danger Rating System.
Fire severity risk
The ACT’s annual Fire Danger Ratings varied greatly over the 1994–95 to 2022–23 period in response to annual temperature and rainfall conditions (Figure 9). Elevated fire severity risk occurs during periods of drought and hot weather, potentially leading to more severe fires (if they were to occur) and an increased difficulty in fire suppression. There is a much lower severity risk of fire during wetter years (for example, 2010–11 to 2011–12 and 2020–21 to 2022–23).

Figure 9: Number of days in Fire Danger Rating categories in the ACT, 1994–95 to 2022–23.
Data sourced from: Environment, Planning and Sustainable Development Directorate.
Note: Fire danger ratings are derived from Fire Danger Index scores. Only includes data from each fire season between 1 October and 30 April, except for 2018–19 which commenced on 1 September. The low to moderate fire danger rating is not shown.
The ACT’s Fire Danger Index and Fire Danger Rating data also shows that:
- Catastrophic ratings are rare in the ACT with only three days occurring between 1994–95 and 2022-23. However, all of these occurrences are linked to the ACT’s most severe bushfires with catastrophic conditions recorded on the first day of the 2003 bushfires (18 January 2003) and two recorded catastrophic conditions in the weeks leading to the Orroral Valley fire in January 2020.
- Extreme ratings are also rare with only eight days occurring between 1994–95 and 2022–23. Three of these occurrences were in the 2019–20 fire season.
- Days of increased Fire Danger Rating occur most often in January, followed by December and February. Increased fire severity risk conditions also occur frequently in November and March.
There is no apparent long-term increase in the overall number of elevated fire danger days, nor an increase in the number of days in the higher risk categories (very high, severe, extreme and catastrophic Fire Danger Ratings). Despite this, climate change is expected to increase the ACT’s fire severity risk in the future (see Climate change).
There has been an increasing number of consecutive fire seasons with elevated fire severity risk in the ACT. This is particularly evident for the 2012–13 to 2019–20 fire seasons which saw an increased number of days with elevated risk conditions over the entire period (Figure 9). Extended periods of elevated fire severity are likely to increase the chance of a significant bushfire occurring. This was certainly the case for the 2020 bushfires which occurred after eight years of elevated risk conditions.
This increasing duration of elevated fire severity risk is also evident in the ACT’s mean Fire Danger Index anomaly which shows that most years since 2000 had a greater fire severity danger than the long-term average (Figure 10). Prior to 2000, there were generally longer periods of reduced fire severity risk that were punctuated by short durations of high risk. However, increased temperatures and drought have led to longer periods of elevated fire severity conditions (see Climate change). The highest mean Fire Danger Index anomaly between 1950 and 2022 occurred in 2019. This is likely a factor in the severity of the 2020 bushfires.

Figure 10: ACT mean Fire Danger Index anomaly (as calculated from the 1961 to 1990 average), 1950 to 2022.
Data sourced from: Bureau of Meteorology, Canberra Airport site, and Environment, Planning and Sustainable Development Directorate.
Fire severity risk 2019–20 to 2022–23
Over the reporting period (2019–20 to 2022–23), the ACT saw highly variable fire severity risk conditions, from the elevated severity risk occurring in 2019–20 which led to the 2020 bushfires, to the greatly reduced risk in the wetter years since 2020 (Figures 9 and 10).
The fire severity risk conditions in 2019–20 were particularly elevated in the month leading up to the Orroral Valley fire and for the first days of the fire (Figure 11). Fire severity risk conditions included two catastrophic and two extreme risk days, seven severe days, ten very high, and nine high risk days. Such conditions significantly increased the severity and spread of the Orroral Valley fire, particularly through increased temperatures and the drying fuel loads.

Figure 11: Number of days in Fire Danger Rating categories in the ACT, 26 December 2019 to 28 January 2020.
Data sourced from: Environment, Planning and Sustainable Development Directorate.