How Wildfires Spread
Why wildfires move the way they do, from ember showers and slope to wind, crown fires, and fire weather.
Most homes in a wildfire ignite from embers, not flames
Wind-driven embers can travel up to two kilometres ahead of a wildfire — most homes that burn are ignited by ember showers long before any visible flame reaches the property.
Read more →Wildfire moves faster up a slope
A wildfire spreads roughly twice as fast on a 10-degree slope as on flat ground — and faster still on steeper terrain, because flames preheat and dry the fuel above them.
Read more →Wind drives ember spread far ahead of the visible fire
A single afternoon wind shift can pivot a fire that has been burning quietly for days straight at a community — wind, not flame height, is what turns evacuation alerts into evacuation orders.
Read more →Crown fires move through the tops of trees and are hardest to stop
A crown fire moves through the tops of trees, often far ahead of the flames on the ground — once a fire reaches the canopy, ground crews can rarely attack it directly.
Read more →Hot, dry, windy days are when wildfires explode
Single-digit relative humidity, sustained wind, and weeks without rain are the conditions behind nearly every major interface fire — the daily fire danger rating quietly tells you when those line up.
Read more →These articles are the same wildfire safety library that lives inside our free app. Browse every category in the safety library, or open the live map to see current fires and alerts across Western Canada and 18 western US states.