Over the past decade, summer temperatures have begun to increase and wildfires have drastically consumed more and more acreage across the Pacific Northwest. We have seen unprecedented burns and in 2017, widespread smoke events like we have not seen in prior years. Within the past 5 years, we have seen our biggest wildfire season ever in Washington state, in terms of acreage burned. 2015 saw 1,137,664 total acres burned across the state, the largest amount of acres burned in recorded history. Despite the widespread smoke events in 2017, it was not one of the years with the highest acres burned, and even with the smoke intrusions, not the worst air quality either. Since 2000, there has been a significant increase in overall acreage burned, and since 2012, an even more significant increase.

Many have wondered if climate change is contributing to bigger fire seasons, but at the current time, it is hard to tell if it really has a direct impact on the fire season itself. Shifting weather patterns not correlated to general climate change have had some effect on our Pacific Northwest fire seasons, in different ways. We have had increasingly wet spring seasons here over the past few years, and although that might seem like a good thing when it comes to fire seasons, in reality, it presents a very big problem. Those big spring rains cause grass and underbrush to rapidly grow and spread. Then, when summer arrives, and like our last few, they have been hotter than normal…which means all that grass and underbrush quickly dries out, becoming a surface fuel for any fires that start. This is a huge concern for increased fire intensity. So while a wet spring might seem ideal, it is actually the opposite when backed with an above average temperature summer.

Other factors that play in to how big fire seasons are, is the amount of lightning that we receive from monsoonal type thunderstorms (minimal rain, excessive lightning type events), number of dry cold fronts that come through, winter snowpack amount, human related fire starts, and how much active fire suppression is available for any given fire year. Monsoonal thunderstorms have decreased over recent years, and although we do get a few boomers along the Cascade Crest that are typically responsible for fire starts here and there, Washington state has seen fewer lightning related starts.

Surprisingly, mountain snowpack seems to have a minimal overall effect on fire seasons unless it has been a very low snowpack year. Active fires have been known to make runs across remaining snowfields when driven by strong winds. Although having a strong snowpack helps drought conditions, it has not seemingly made a big difference on number of acres burned on years when it is higher versus years in which it is lower. The only caveat is, unless the snowpack is extremely low. It’s worth noting that both our worst fire season and snowpack occurred in 2015, and there may actually be some relationship between extremely low snowpack and increased fire danger. However, due to our small sample size, it’s too early to say whether there is a relationship between these two. The explosive 2015 fire season was one of the lowest snowpack seasons, and one of the hottest summers on record in Washington state. On the other hand, a few of the additional largest fire seasons came after high snowpack years, so it is difficult to determine if snowpack ultimately makes any difference in the end result. The snowpack is also melting earlier in many cases, which contributes to a longer fire season.  

Image Credit: Climate Central – www.climatecentral.org

Temperatures ultimately seem to have the highest overall correlation to fires and number of acres burned. Hotter summers favor more acres burned, and wetter springs provide more fuel, resulting in more acres burned. When you pair hotter temperatures with any type of additional fire weather pattern, you can get explosive fire growth on any new fires or any already present. Winds of any type are a huge driver when it comes to fires, especially when temps are hot and humidity is low.  

Image Credit: Predictive Services, National Interagency Fire Center

As we head into the 2018 summer fire season, we have already seen some small spot fires around the Pacific Northwest as of the last few weeks. A 15-acre fire occurred in Southwestern WA in mid-April, and officials are preparing for another intense season. We are coming off another very wet spring, which raises increased concerns for prolific grasses and underbrush, providing excessive fuels for any fires that do occur. The Climate Prediction Center just released their 3-month outlook for May-June-July, and it is not particularly encouraging for a mellow fire season. The Pacific Northwest is expected to see temperatures significantly above normal, and it is expected to be around 33% drier than normal.

Image Credit: NOAA Climate Prediction Center

A hot and dry start to fire season raises numerous concerns for later in the season, although this year it is not expected to pick up drastically until later in the summer once fuels dry out. Washington’s Department of Natural Resources is gearing up for the season by keeping resources at the ready, holding various fire trainings, and working to improve coordination to help fight these larger fires more effectively.