The string of fast-moving fires that ignited across eastern Washington and Oregon this week traces directly to a dangerous but predictable fire weather event: a cold front passage that brought strong, gusty winds along with critically low relative humidity values to a landscape already primed for rapid fire spread after a dry spring.

The Red Flag Setup

The National Weather Service office in Pendleton issued a Red Flag Warning for much of eastern Washington and northeast Oregon on Tuesday, June 16, effective from 10:00 a.m. through 11:00 p.m. PDT. The warning cited a dangerous combination of:

  • Wind gusts of 25–45 mph with higher gusts on ridgetops and in channels
  • Relative humidity values dropping into the single digits during peak afternoon heating
  • Fine and large fuel moisture at critically dry levels following months of below-normal precipitation

A Red Flag Warning means conditions are ideal for the rapid ignition and spread of wildfire. When forecasters see this combination of wind, low humidity, and dry fuels, any spark — from a vehicle, power line, or lightning strike — has the potential to escape initial attack and grow into a large fire before crews can respond.

Why Fuels Are So Dry

The Pacific Northwest has experienced a difficult combination of weather patterns this year. Below-normal snowpack in the Cascades and Blue Mountains meant less soil moisture recharge during the spring melt season. Much of eastern Washington and Oregon received below-average precipitation in March through May, and early summer heat has accelerated fuel curing.

Cheatgrass and other annual grasses — which dominate much of the shrub-steppe landscape east of the Cascades — had already cured weeks ahead of schedule, creating a continuous carpet of highly flammable fine fuels across the Columbia Basin and Palouse. Large fuel components (timber and heavy brush) also show below-average moisture levels in fire weather monitoring networks, contributing to extreme fire behavior potential.

Central Oregon Also Impacted

A separate Red Flag Warning was issued by the NWS Pendleton office for the Central Oregon Mountains (Fire Weather Zone 700) on June 17, effective from 11:00 a.m. to 9:00 p.m. PDT, as gusty outflow winds and low humidity spread southward behind the front. Fire officials in Central Oregon urged residents and recreationists to avoid any potential ignition sources.

What’s Ahead

The NWS forecast for eastern Washington and Oregon through the weekend calls for continued warm and dry conditions, with temperatures running 5 to 10 degrees above normal. Afternoon relative humidity values will remain below 20% in many locations. Winds will diminish compared to the frontal passage, reducing the most extreme spread risk, but fire danger will remain at Very High to Extreme across the region.

Fire weather watches or warnings may be reissued next week if another weather system brings wind events to the region. Residents, ranchers, and outdoor recreationists throughout eastern Oregon and Washington should remain vigilant and avoid any activities that could cause ignitions — no burning, no target shooting with steel-core ammo, and no parking in tall dry grass.