Multiple large wildfires in the Cascades and the mountains of northeast Washington produced copious quantities of dense smoke through much of the month of August. The Methow Valley in particular was bracketed by two large fires, the McCleod fire to the north and the Crescent Mountain Fire to the south. Smoke from these fires produced nearly continuous Unhealthy air quality and occasionally Hazardous air quality in Twisp and Winthrop between August 3rd and August 27th, when a cold front passed through and ventilated the region.
The communities of Omak, Tonasket, Republic and Colville also suffered long periods of Unhealthy air quality conditions from these fires and the Boyds Fire near Kettle Falls, as well as occasional smoke intrusion from large wildfires in British Columbia.

Dense Smoke in OKANOGAN HIGHLANDS, WASHINGTON
From 03-AUG-18 00:00:00 to 27-AUG-18 00:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Other Federal Agency

An air quality sensor in Nespelem recorded periods of Unhealthy air quality due to smoke from area wildfires through much of August. Air quality deteriorated into the Hazardous range for much of August 19th, and fluctuated between Unhealthy and Unhealthy for Sensitive Groups until a frontal passage brought breezy conditions and some rain on August 27th.

Dense Smoke in OKANOGAN HIGHLANDS, WASHINGTON
From 03-AUG-18 00:00:00 to 27-AUG-18 15:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Other Federal Agency

An air quality sensor in Inchelium recorded periods of Unhealthy air quality due to smoke from area wildfires through much of August. Air quality deteriorated into the Very Unhealthy and Hazardous range from August 19th through August 20th before marginally improving until a cold front passage on August 27th.

Dense Smoke in OKANOGAN VALLEY, WASHINGTON
From 03-AUG-18 00:00:00 to 27-AUG-18 00:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Other Federal Agency

The air quality sensor at Omak recorded Unhealthy air quality through most of the month of August. On August 19th and 20th air quality deteriorated into the Hazardous range before moderating back to Unhealthy until a cold front passage cleared out the smoke on August 27th.

Dense Smoke in OKANOGAN HIGHLANDS, WASHINGTON
From 03-AUG-18 00:00:00 to 27-AUG-18 15:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Other Federal Agency

An air quality sensor in Republic recorded almost continuous Unhealthy air quality due to smoke from area wildfires through much of August. Air quality deteriorated into the Very Unhealthy and Hazardous range from August 19th through August 20th. Air Quality fluctuated between Unhealthy and Very Unhealthy until a cold front passage on August 27th ventilated the region.

Dense Smoke in NORTHEAST MOUNTAINS, WASHINGTON
From 03-AUG-18 00:00:00 to 27-AUG-18 16:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Other Federal Agency

An air quality sensor in Colville recorded occasional periods of Unhealthy air quality with a few spikes into the Very Unhealthy range due to smoke from area wildfires through much of August.

Dense Smoke in EAST SLOPES NORTHERN CASCADES, WASHINGTON
From 03-AUG-18 00:00:00 to 27-AUG-18 15:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Other Federal Agency

An air quality sensor at Winthrop recorded Unhealthy air quality from August 3rd through August 27th with occasional spikes into the Very Unhealthy category. This sustained period of Unhealthy air quality was the result of large nearby wildfires and was only alleviated with a breezy cold front passage on August 27th.

Dense Smoke in EAST SLOPES NORTHERN CASCADES, WASHINGTON
From 03-AUG-18 00:00:00 to 27-AUG-18 15:00:00 (PST-8)
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Other Federal Agency

An air quality sensor at Twisp recorded Unhealthy air quality from August 3rd through August 27th with occasional spikes into the Hazardous category. A cold front passage on August 27th brought breezy westerly winds which ventilated the area.