The Minnesota Pollution Control Agency extended an air quality red alert — considered unhealthy for all populations — until 11 p.m. Monday for the Twin Cities and much of southern Minnesota due to lingering wildfire smoke.

The affected area includes the Twin Cities metro, Albert Lea, Marshall, Worthington, Rochester, Winona, Mankato and the tribal nation of Prairie Island, the agency said in a news release.

Minnesotans were urged to keep windows closed overnight as wildfire smoke from Canada wafted into the state. The first air quality alert of the year was an unwelcome sign for many on the heels of one of the first perfect-weather weekends of the season.

Wondering how to stay safe or if we'll be in for another summer of smoky skies? Here's what to know.

Keep an eye on air quality alerts

The Environmental Protection Agency's AirNow site offers real-time readings of the air quality index (AQI) and also shows where fires are burning and where smoke is spreading. Purple Air, a company that makes air sensors, also has a network of AQI sensor readings at map.purpleair.com. The Minnesota agency posts its current conditions here.

Will this summer be as bad as last year?

Canadian wildfires were not expected to erupt this quickly this spring, MPCA Research Scientist David Brown said Monday. The agency expects there will be more air quality alerts this summer compared to that of a typical year, but still fewer than the 21 alerts issued last year.

Minnesota typically issues five to seven air quality alerts a year, often due to wildfire smoke. Given the conditions, forecasters believe the state will likely need to issue at least seven alerts by the end of the summer, state meteorologists said last week.

What do red alerts look and feel like?

The sky may look smokey, the air will be hazy and you may smell smoke. Anyone can experience irritated eyes, nose and throat, coughing, chest tightness or shortness of breath from the fine particles in the air. Sensitive groups may experience more serious health effects possibly leading to an asthma attack, heart attack or stroke.

Outdoor physical activities should be reduced. Everyone should consider rescheduling or postponing prolonged or vigorous outdoor activities, according to the MPCA.

What is a 'sensitive group?'

Sensitive groups include people with asthma, chronic obstructive pulmonary disease (COPD), heart disease, high blood pressure, diabetes, pregnant people, children and older adults.

Will a window air conditioner bring smoke into my home?

On bad air days, make sure the unit is recirculating. Users should make sure the unit is well insulated in the window — any gaps or cracks can let pollution sneak in.

Indoor air filters with HEPA-compliant screens can also help. It's possible to make your own version, by taping filters to a box fan.

What about masks?

Experts advise that well-fitting respirators that are designed to filter tiny particles, like an N95, will offer protection for those who have to be outside. The tiny smoke particles will easily penetrate thinner fabrics.