The temperature, relative humidity, wind speed and precipitation data collated from weather stations is used to determine fuel moisture and fire behaviour indices through the fire weather index component of the Canadian Forest Fire Danger Rating System (CFFDRS). A map of B.C. showing major towns and other features can be found at the bottom of this page for reference purposes.
Note: Where discrepancies exist between the colour display on the weather maps and the numerical values posted for the weather stations, the posted numerical values shall take precedence for the purpose of implementing the Wildfire Regulation.
The amount of precipitation has a significant impact on the moisture level in the fuels. Precipitation of 0.5 mm or less tends to be intercepted by the forest canopy preventing it from reaching the fuels on the forest floor.
Relative humidity refers to the ratio, in percent, of the amount of moisture in a volume of air to the total amount of moisture which that volume of air can hold at a given temperature and atmospheric pressure. The amount of moisture in the air affects the level of moisture in the fuels. Dry air (low relative humidity) will tend to dry out fine fuels, while moist air (higher relative humidity) will tend to add moisture to fine fuels.
Wind dries fuels by moving moisture laden air away from the fuels and replacing it with drier air which can then draw up more moisture, thereby continually drying the fuels. Wind speed influences the rate of fire spread. Burning embers can also be transported by wind and blown onto new fuels ahead of a fire.
Temperature also has an impact on fuel moisture and fire behaviour. Fuels heated by the sun will ignite more easily and burn faster than cooler fuels, while warmer air, which can hold more moisture than cooler air, can lead to increased drying of fuels.
Due to the significant amount of information displayed on fire weather maps, little other detail is displayed. Therefore, it can be helpful to compare the weather maps to a more detailed map (below) for orientation.