The 30-30-30 rule: Predicting wildfires activity using weather

Have you ever heard of the 3030 Thirty rule? Well, it has to do with predicting wildfire activity. In particular the weather conditions that give a fire the best chance of growing. If predicted correctly, that can have a hugely beneficial impact a controlling wildfires. So let’s break it down. The 3030 Thirty rule is something that is trying to be simple enough to make you aware of when there’s the potential for extreme fire behavior. Temperatures 30° or higher, relative humidity 30% or lower, and wind speeds of at least 30 kilometers an hour create what experts call crossover. That is the relative humidity level equaling or crossing over the ambient air temperature. These conditions Preheat vegetation towards combustion, dry vegetation out through evaporation, and of course allow for the spread of flames and embers. A prime example of this was seen in Fort McMurray in 2016 when on May 3rd temperatures soared above 30, humidity dropped as low as 12%, and winds gusted to more than 70 kilometers an hour. It’s a good ballpark to be aware of when things might get a little spicy beyond the weather. There are other conditions that will allow a fire to grow more easily, for example in steeper terrain if fire can spread quickly with uphill fuel sources closer to the flames while wind in that type of terrain tends to blow uphill. But still, an accurate weather forecast can help get the resources in place to stop a high risk wildfire. In its tracks, and we get those those inputs correctly. We can do a fairly good job, but it’s it’s quite challenging to really be confident. As for ideal firefighting conditions, officials hope for high humidity and low wind, even on a hot day. Fires can be easily suppressed if the fuel sources aren’t being dried out by the atmosphere. And of course, even light rain like this can help soak through that vegetation, dampening wildfire activity from the ground up if it rains for long enough.