By January, many people in the US are quite tired of the cold and snows of winter. When spring arrives with warmer temperatures, they are often elated. Trees and bushes burst into leaves and grasses explode in growth. However, as the spring continues on into summer the story often changes. Part of this is because of the increased risk of wildfires.
Wildfire needs three things to get started and to rapidly get out of control; air or oxygen, combustible fuel, and a heat source. Air is seldom an issue as we are surrounded by it. A heat source isn’t hard to find, either. A carelessly tossed cigarette or match, the exhaust from a car, fireworks, a lightning strike, and even glass acting as a magnifying glass can produce the heat needed in order to get the fire started.
Neither of these are particularly dependent on the season. However, the third, fuel, is.
Fuel actually isn’t dependent on the season, either. How combustible it becomes can be, though. The moisture of winter makes the fuel difficult to burn. The leaves and grasses of spring are also moist, usually. In the summer, the increased temperatures and often dropping humidity in the air do have a great impact.
More heat means that the leaves, grasses and even wood can dry out quickly. The air is often dry enough to absorb the moisture that was formerly in the plants. The drier they become, the more prone they are to the ravages of fire. They often also mat down or fall to the ground, increasing the danger.
All that is then needed is a simple spark to ignite a raging conflagration. It doesn’t end there, though.
The dry air and dust particles, coupled with the heat hitting the ground, produce updrafts. As the moisture is taken from the ground and plants, it is drawn up high into the air, quickly forming clouds. If the conditions are right, these often become thunder or lightning pods.
Friction in the air, partly from dust, can charge them with tremendous amounts of energy. When the difference between the electrical energy of the thundercloud and the ground becomes great, a lightning bolt is released, often connecting with the ground or trees on it. The bolts may look large, however they usually aren’t. Still, they produce a tremendous amount of heat.
Hitting the ground or a dried out tree, the lightning can easily cause enough heat to cause a hot flame which can rapidly spread through the abundant fuel. According to a former US Forest service spokesman, Steve Trulove, “Lightning strikes are easily the biggest ignition source for forest and wildfires in the West.”
The thunder storms also produce a catalyst: Wind. The updrafts often cause gusty ground wind, which can fan almost any blaze that has begun. This can in turn cause the fire to spread so quickly that that it becomes large by the time it is even spotted. The result is often catastrophic and devistating.
Fires can happen at almost any time of year. However, in the summer, the conditions are most often right for a wildfire that is difficult to contain and to put out. Extra care is in order. A person may not be able to prevent lightning strikes, but they can keep from adding to the problem, and can help if any fire that is spotted is promptly reported.
Sources:
US Forest Service
Oregon Department of Forestry
US Park Service
Special mention:
Greg Thomas, forest fire fighter, dec. while battling a blaze
