Ever wonder what the various DNR Fire Danger Ratings mean? The material below explains the criteria used for each danger status. Additional information can be found at the DNR Fire Danger and Outdoor Burning web site.
Fires do not start easily and those that do start tend to spread slowly. Fires in forests tend to spread irregularly with flames of less than one foot. Fires in dry grass spread steadily with flames slightly less than or equal to the height of the grass. Shrubs within the grass may not burn readily. Embers from the fires rarely start additional fires and tree crowns generally do not ignite.
Fires start somewhat readily to rapidly. Fires in forests spread slowly to moderately quickly with flames of 1-3 feet. Crowns of trees with branches close to the ground may ignite (torching) but fires rarely spread far in the tree crowns. Fires in dry grass spread moderately quickly to quickly with flames up to 2 times the height of the grass, especially if conditions are windy. Some shrubs within the grass burn readily. Embers from the fires may start additional fires (spotting) a short distance from the main fire. Unattended campfires may begin to creep away from the fire ring or fire pit.
Fires start readily and spread quickly. Fires in forests can ignite small groups of trees (group torching) and spread for short distances in tree crowns (short crowning runs). Flames in the surface part of the fire can easily exceed 4 feet and may exceed 8 feet. Fires in dry grass spread very quickly with flames of 10 to 20 feet, especially where shrubs are also burning. Spotting is common and can occur some distance from the main fire. Unattended campfires are likely to escape a fire ring or fire pit and sparks are likely to start fires in dry grass and needles.
Fires start readily and spread very quickly. Crowning runs are common and fire spread through tree crowns for some distance (crown fire) is possible. Flames in the surface part of the fire can easily exceed 8 feet and may exceed 12 feet. Fires in dry grass and shrubs spread very quickly with flames over 20 feet likely. Torching and short crowning runs are possible in juniper, where it is present. Spotting is very common and occurs some distance from the main fire. Unattended campfires are very likely to escape and sparks are very likely to start fires in dry grass and needles.
Fires start readily and spread furiously, and burn intensely. All fires are potentially serious. Development into high intensity burning will usually be faster and occur from smaller fires than in the very high fire danger class. Every fire start has the potential to become large. Expect extreme, erratic behavior. No yard waste burning should take place in areas with extreme fire danger. Fire restrictions are generally in effect.