Yosemite National Park wildfire smoke forecast
The map above shows NOAA HRRR-Smoke near-surface PM2.5 for the next 48 hours, updated hourly, with active fires from NIFC and live AQI from EPA AirNow monitors. It opens over Yosemite National Park.
Yosemite Valley is a glacial trough at about 4,000 feet with walls rising more than 3,000 feet above the floor, which makes it one of the most effective smoke traps in any American national park. The rest of the park climbs to over 8,000 feet at Tuolumne Meadows and above 9,900 feet at Tioga Pass, and those elevations frequently sit above the layer holding in the valley.
Where the smoke comes from
Fires in the Stanislaus and Sierra national forests on either side of the park are the main suppliers, along with fires inside the park itself. Central Valley air also moves up the Merced and Tuolumne canyons on afternoon upslope flow, carrying smoke that originated a hundred miles west.
How long it lasts
The valley clears last. Upslope flow fills it during the day and drainage flow keeps it in overnight, so a valley visitor and a Tuolumne visitor can experience completely different air on the same afternoon. Checking the forecast for the specific part of the park you are going to matters more here than in almost any other park.
Past smoke events
The 2013 Rim Fire burned over 250,000 acres on the park's western edge. The 2018 Ferguson Fire closed Yosemite Valley for about three weeks at the height of summer, the longest such closure in decades, and the 2020 Creek Fire filled the region again.
Trails and viewpoints
The valley floor loop, Mist Trail, and Half Dome sit in the trapping zone. Tioga Road, Tuolumne Meadows, and the high country are the reliable alternative during a valley smoke episode, and Glacier Point at 7,200 feet often looks down on the layer rather than sitting in it.
Reading the map
Use the layer toggle to compare NOAA HRRR-Smoke with the ECCC FireWork model. When the two disagree, treat the higher reading as the cautious call.
Near-surface is the product that maps to what you breathe and to AQI, not the high-altitude column that only tints the sunset. A sky that looks bad and a monitor that reads fine are usually both correct, and they are describing different layers of air.