Drivers and Impacts of the Record-Breaking 2023 Wildfire Season in Canada

Abstract

The 2023 wildfire season in Canada was unprecedented in its scale and intensity, spanning from mid-April to late October and across much of the forested regions of Canada. Here, we summarize the main causes and impacts of this exceptional season. The record-breaking total area burned (~15 Mha) can be attributed to several environmental factors that converged early in the season: early snowmelt, multiannual drought conditions in western Canada, and the rapid transition to drought in eastern Canada. Anthropogenic climate change enabled sustained extreme fire weather conditions, as the mean May-October temperature over Canada in 2023 was 2.2 °C warmer than the 1991-2020 average. The impacts were profound with more than 200 communities evacuated, millions exposed to hazardous air quality from smoke, and unmatched demands on fire-fighting resources. The 2023 wildfire season in Canada not only set new records, but highlights the increasing challenges posed by wildfires in Canada.

Fig. 1. Overview of 2023 fire season.

Infographic showing NBAC-M3 mapped fires, regional area burned and timeline and location of key events that occurred during the Canadian 2023 wildfire season. Background texture designed by Freepik (www.freepik.com).

Fig. 2. Annual area burned time series for Canada.

Annual area burned for Canada from the National Burned Area Composite (NBAC; 1986–2022) and NBAC-M3 (Natural Resources Canada, 2023b) datasets. During 2023, 15 Mha burned, compared to the annual mean of 2.1 Mha (1986–2022, dashed line). The next largest annual area burned occurred in 1989 with 6.7 Mha.

Fig. 3. Early 2023 fire season conditions for Canada.

a timing of snow melt; b snow melt timing departure (days) from historical average (2004–2022); c mid-point timing of maximum Root Zone Soil Moisture (RZSM) drying in any two-week period between May and July; d the corresponding maximum RZSM drying amount; e standardized anomalies of the May Drought Code (DC); f standardized anomalies of the June DC. Data sources are described in methods.

Fig. 4. 2023 fire season weather anomalies and rankings.

2023 fire season (May–October) anomalies relative to baseline period (1991–2020) for: a 2-m temperature c total precipitation; e vapor pressure deficit (VPD); 2023 fire season (May–October) mean value ranking during period 1940–2023 for b 2-m temperature; d, total precipitation; and f VPD. Data derived from the ERA5 reanalysis.

Fig. 5. Daily area burned and extent of extreme fire weather during 2023.

a Daily area burned in 2023, by province/territory estimated from interpolated day of burn for fires ≥ 500 ha; scale was exaggerated (e.g., × 2) in areas with comparatively low area burned; and b the daily forested area in each province/territory with FWI values exceeding the 95th percentile of FWI (during the fire season). Nunavut is excluded from the plots due to its low total area burned and low forest cover.

Fig. 6. Extreme fire weather conditions during 2023.

a Total number of days exceeding local 95th percentile of FWI for 2023; b Anomaly in total number of days exceeding local 95th percentile of FWI for 2023 relative to baseline period (1991–2020); c Proportion forested area exceeding local 95th percentile of FWI (black) compared with mean (red) values for 1991–2020 (confidence intervals shaded for 5th and 95th percentiles); d Mean proportion forested area exceeding local 95th percentile of FWI during fire season (May–September) for each year (1940–2023).

Fig. 7. Fire size and timing during the 2023 fire season.

a Left: number of fires > 50k ha for each fire size class for historical period (1986–2022, annual mean) and for 2023; Right: proportion of total area burned for each fire size class for 1986–2022 and 2023; b Fire size as function of potential spread days (extreme fire weather days; FWI₉₅) for western Canada (west of −85 deg longitude) and eastern Canada (east of −85 degrees longitude). c Distribution of fire sizes by start month for all fires > 1000 ha. (colored outliers correspond to fires > 100,000 ha). d Cumulative daily area burned for fires starting in each month between May–October.

Fig. 8. Wildfire smoke and evacuation impacts for 2023.

a The number of days in 2023 with daily mean PM2.5 > 27 μgm⁻³; b the maximum daily value of PM2.5 that occurred during 2023; c the number of air quality bulletins each month issued by Environment and Climate Change Canada between 2017 and 2023 (Health and Air Quality Forecast Services Program, MSC-ECCC, December 2023); d The number of annual evacuation orders and evacuees from 1980–2023 using data from the Canadian wildfire evacuation database.