The Montana Department of Environmental Quality issued an air quality alert for Lewis and Clark County and more than two dozen surrounding counties, in effect until 9 a.m. Tuesday, July 29. The alert, relayed through the National Weather Service office in Great Falls, covers a broad swath of central and western Montana and is tied to elevated particulate levels — most likely from wildfire smoke — compounding under the same heat system straining the regional electrical grid this week.
Lewis and Clark County sits squarely inside the alert zone, which stretches from Beaverhead County in the south to Hill and Phillips counties in the north and includes Missoula, Cascade, Silver Bow, and Ravalli counties. The range of the alert reflects how widely smoke can travel under the high-pressure systems that typically accompany summer heat waves in Montana, trapping particulates at lower elevations rather than allowing them to disperse.
Residents with respiratory conditions — including asthma, COPD, and heart disease — are advised to limit time outdoors, especially during afternoon hours when ozone and particulate concentrations tend to peak. Children and older adults are also considered higher-risk groups during air quality events. Helena-area residents can check current air quality index readings at AirNow.gov or through the DEQ's Montana Air Quality Index page.
The alert runs concurrently with the federally declared grid emergency for the region. Health officials generally recommend keeping windows closed and running air conditioning with a clean filter as the most effective way to reduce indoor particulate exposure — advice that, during a heat event, requires residents to weigh air quality against the risk of heat indoors for those without reliable cooling.