Wildfire smoke is expected to harm air quality in Maine through the Fourth of July weekend, and the ongoing heat wave could compound the effects.

The Maine Department of Environmental Protection warned Thursday that wildfire smoke will likely spark a rise in particle pollution statewide to levels that are unhealthy for sensitive groups — and potentially unhealthy for all people for short periods.

An air quality alert is in effect through Sunday for the entire state as smoke from neighboring Quebec moves into Maine.

The alert comes after the Maine DEP warned Wednesday that ground-level ozone was expected to reach levels that are unhealthy for sensitive groups. That alert also cautioned that wildfire smoke would create “moderate” particle pollution.

Large wildfires are raging in Canada and near the Colorado-Utah state line. Maine is sometimes dubbed “the tailpipe” of the U.S. because its location in the far Northeast often places it downwind for pollutants moving in from the west.

The Maine DEP advises that when smoke reduces visibility or provides a notable scent, sensitive groups — such as people with heart or lung conditions, outdoor workers, older adults and children — should reduce prolonged or heavy exertion. It’s still OK to go outdoors, but frequent breaks are recommended.

The department also recommends keeping windows closed and circulating air with fans or air conditioning. Those with asthma are advised to keep medication readily available, while those with heart disease should monitor for palpitations, fatigue and shortness of breath.

The particle pollution could still pose issues, even if you’re not sensitive to low-quality air. The agency said even healthy adults might encounter coughing, throat irritation, shortness of breath or mild chest discomfort.

The ongoing heat — potentially nearing record levels Thursday — may compound the impact of the smoke.

“Whether you’re outside for work or to enjoy the holiday festivities this week and weekend, it’s important to take precautions against sun exposure, dehydration, heat exhaustion, and heat stroke,” the Maine DEP said in its warning.