Rain and Cooler Temperatures - What Comes Next for Fire Season?
Precipitation totals over the past 72 hours have favored southwest Washington, the Olympics, and the Blue Mountains. In fact, windward portions of the Olympic Mountains recorded 2-4 inches of rain from this system so far. Rain amounts of 1-2 inches were also observed in portions of the south Cascades.
Even with the pattern change to cooler and damp, the map below highlights portions of state that received less than 0.25" of rain this week. Dry spots focused in the lowlands of northwest Washington and lower elevations east of the Cascade crest. The Little Giant Fire notably received minimal precipitation.
In the near-term, the fire environment is slowing quite a bit even for areas that haven't received a lot of rain. That is because cooler temperatures and higher relative humidity allows fuels to absorb moisture from the air and become less flammable. Looking ahead, additional light precipitation is expected this weekend but primarily in areas that have already received it. For example, the Little Giant Fire has not received a quarter inch of rain yet and only has around a 20% chance to receive a quarter inch of additional rain. Regardless, near to below normal temperatures and minimal wind will keep the fire environment relaxed this weekend.
Then, a gradual warming and drying trend is on the horizon for the middle of next week, followed by a lot of uncertainty in the weather pattern mid-month. With the warming temperatures next week, areas that missed out on significant rain should quickly return to a state that would support fire spread. This is especially true in lighter, flashy fuels such as the grass and sagebrush of the Columbia Basin. In contrast, heavily forested areas that received a lot of rain will struggle to return to conditions that prompt any concern for significant wildfire spread (e.g. Olympic mountains).
In general, we are entering the time of year where emerging large wildfires just aren't very common across the state. In fact, for the past 25 years (2001-2025) Washington only averages about one 1000+ acre fire annually beginning on or after September 10.
That said, existing forest fires like Little Giant could still grow and produce increased smoke if favorable fire weather conditions return over the next few weeks. Given the uncertainty in the forecast, it is certainly possible that fire activity could increase again -- just probably not to August levels.
Air Quality Improvement
Air quality has improved in recent days, even for areas closer to the large fires in the Cascades. Between August 22 and September 1, monitors in Cle Elum, Leavenworth, Peshastin, Entiat, and Chelan were experiencing almost daily periods of air quality reaching UNHEALTHY FOR SENSITIVE GROUPS to UNHEALTHY, with a few spikes into VERY UNHEALTHY or HAZARDOUS observed.
Since Wednesday, however, hourly readings have primarily been GOOD to MODERATE.
In general, minimal changes are expected in the near-term and most communities across the state will experience GOOD air quality for the holiday weekend. If you've been dealing with smoke and finally have better air quality, it's a great time to open those windows! Areas very close to large fires in the Cascades, however, will still experience periodic smoke impacts -- particularly in the morning hours.
