Wildfire smoke drifting in from Nevada and a Red Flag Warning covering the Wasatch Mountains are creating dangerous conditions this weekend for canyon-adjacent neighborhoods in Cottonwood Heights and Holladay.

The National Weather Service issued the Red Flag Warning for Fire Weather Zone 479, which includes the Wasatch Mountains directly above both cities, effective Sunday, Aug. 2, through 10 p.m. MDT. Southwest winds of 10–20 mph, gusting up to 35 mph, combined with relative humidity as low as 5–10% at lower elevations, create conditions where any new fire start or existing blaze could spread rapidly, the agency warned.

The warning is a separate alert from the Extreme Heat Warning issued for the weekend. While the heat warning targets human illness risk, a Red Flag Warning specifically flags critical fire weather that threatens wildland areas like Big Cottonwood Canyon.

Smoke settles over the Wasatch Front

Nevada wildfire smoke pushed air quality on the Wasatch Front into the "Unhealthy for Sensitive Groups" category on Sunday, Aug. 2, according to ABC4 Utah. ABC4 weather forecaster Seth Sanders advised residents prone to respiratory illness to limit time outdoors and avoid strenuous activity while the smoke lingers.

"On Monday, temperatures finally dip back down to average across northern Utah, which hasn't happened very often in the last month," Sanders said in ABC4's Sunday forecast.

Multiple wildfires were already burning across Utah as of Saturday, Aug. 1, including the 10,300-acre Widemouth 2 Fire in Millard County and the Johnson Canyon Fire in Box Elder County, which reached 700 acres and triggered evacuation-ready status for the town of Portage, KSL reported. Saturday's high at Salt Lake City International Airport hit 105°F, matching the record high for Aug. 1.

Brief relief, then more heat

Northern Utah valleys should see highs drop to the low-to-mid 90s on Monday, Aug. 3, and Tuesday, Aug. 4. Triple-digit temperatures are forecast to return by Thursday, Aug. 6, and persist into the following weekend.

No specific fire restrictions or trail closures for Big Cottonwood Canyon had been announced as of Sunday evening, but the NWS warning means conditions in the canyon are ripe for rapid fire spread. Residents heading up-canyon for hiking or picnicking should check current conditions before going and avoid any activity that could spark a flame.

What residents should know

• Fire danger: Critical through Sunday, Aug. 2, evening; avoid open flames, off-road driving, or dragging chains on pavement near wildland areas.
• Air quality: Unhealthy for sensitive groups Sunday; those with asthma or respiratory conditions should stay indoors.
• Heat: Brief dip Monday–Tuesday (low 90s), then triple digits return Thursday.
• Canyon access: No closures announced, but fire conditions are elevated in the Wasatch Mountains zone.