Smoke from wildfires in Western Canada drifted across the Midwest and the Northeast of the United States on Monday, blotting out blue sky and sun and blanketing dozens of cities with unhealthy air that triggered warnings to limit the time spent outdoors.

It was the second time in less than a month that the borderless impact of climate change could be felt with a breath. In June, heavy smoke from Quebec wafted into the East Coast, and blew from New York City, past Washington, as far west as Minnesota.

This week, as nearly 900 wildfires burned across Canada, the smoke came from fires in the western part of the country, billowing into its southern neighbor across a wide trail.

By 1 p.m. Eastern time, about 71.6 million people in 29 states were affected by the shifting, migrating smoke, according to estimates based on information from the National Oceanic and Atmospheric Administration and LandScan, a population database.

“Unfortunately, the wildfire smoke will begin to make a return to the region to start the new week,” according to the National Weather Service in the Philadelphia area.

Air quality alerts, ranging from moderate to very unhealthy, were issued by government agencies from Montana to the Dakotas and parts of other states, including Nebraska, Alabama, Tennessee, Ohio, North Carolina and along the Northeast.

Residents were advised to take precautions, from limiting outdoor activities to covering up with masks. In Chicago, where the air quality deteriorated through the weekend, Mayor Brandon Johnson warned children, older residents and those with heart or lung disease to limit outdoor activity.

“We are acutely aware that the recent weather events prominently impacting our City this summer are the direct result of the climate crisis,” he said.

Gov. Kathy Hochul of New York on Sunday issued air quality health advisories for Monday. The air quality in parts of upstate New York was expected to reach unhealthy levels for all residents, while conditions in the Lower Hudson Valley, New York City and Long Island were expected to be unhealthy only for sensitive groups.

“New Yorkers should once again prepare for smoke from the wildfires in Western Canada to impact our state’s air quality this week,” Ms. Hochul said in a statement, adding that officials were activating emergency notifications on roads and public transit systems and making sure that masks were available for distribution in counties across the state.

The air quality index in Rochester was already at 141 early Monday, while Buffalo’s was at 116. New York City officials said that conditions, which are considered unhealthy for sensitive groups, could persist for the initial part of the week.

The index runs from 0 to 500; the higher the number, the greater the level of air pollution. An A.Q.I. of 201 or more is considered very unhealthy.

So far, the air quality warnings were not as bad as they were in early June, when there were readings above 400 on the East Coast, signaling a hazardous level.

But by 10 a.m. Eastern time on Monday, cities across the Midwest were reporting some of the worst air quality in the country, according to the Environmental Protection Agency Billings, Mont., and Fort Wayne, Ind., had an A.Q.I. of 161, while the Cleveland area was at 157.

The forecast is expected to cause “unhealthy for all” conditions in the areas closest to the Canadian border, according to AirNow, a website run by the E.P.A., which oversees air quality across the United States.

The Ohio Environmental Protection Agency said its advisory was in effect through Monday. In the southwestern region of the state, residents were told to limit use of their vehicles, to refrain from mowing lawns and to avoid burning firewood and yard waste.

Local officials also advised residents to limit outdoor activity or using their cars, and to wear masks. The message was repeated from Buffalo — where Mayor Byron W. Brown told residents to take precautions — to Chicago, where an air quality alert was in effect through Sunday night.

In Pennsylvania, where the Department of Environmental Protection issued a statewide “code orange” alert, officials suggested residents and businesses help by limiting burning of leaves, trash, and other materials, and avoiding the use of gas-powered lawn and garden equipment.

Wildfire smoke from Canada is forecast to linger through Tuesday, propelled by northwesterly winds, the Weather Service said.

Early last month, the level of particulate matter in the air from smoke became so unhealthy that many U.S. cities set records. At points, it was hazardous to breathe everywhere from Minnesota and Indiana to sections of the Mid-Atlantic and the South.

Visibility decreased to startling degrees in cities, including New York, Toronto and Cincinnati. In some places, smoke from the fires blanketed the sky in an orange haze. That smoke could be traced to wildfires burning in Quebec.

Jon duSaint, a retired software engineer, recently bought property near Bishop, Calif., in a rugged valley east of the Sierra Nevada. The area is at risk for wildfires, severe daytime heat and high winds — and also heavy winter snowfall.

But Mr. duSaint isn’t worried. He’s planning to live in a dome.

The 29-foot structure will be coated with aluminum shingles that reflect heat, and are also fire-resistant. Because the dome has less surface area than a rectangular house, it’s easier to insulate against heat or cold. And it can withstand high winds and heavy snowpack.

“The dome shell itself is basically impervious,” Mr. duSaint said.

As weather grows more extreme, geodesic domes and other resilient home designs are gaining new attention from more climate-conscious home buyers, and the architects and builders who cater to them.

The trend could begin to dislodge the inertia that underlies America’s struggle to adapt to climate change: Technologies exist to protect homes against severe weather — but those innovations have been slow to seep into mainstream homebuilding, leaving most Americans increasingly exposed to climate shocks, experts say.

Riding out the storm

In the atrium of the Smithsonian’s National Museum of American History, students from the Catholic University of America recently finished reassembling “Weatherbreak,” a geodesic dome built more than 70 years ago and briefly used as a home in the Hollywood Hills. It was avant-garde at the time: roughly a thousand aluminum struts bolted together into a hemisphere, 25 feet high and 50 feet wide, evoking an oversize metal igloo.

The structure, designed by Jeffrey Lindsay and inspired by the work of Buckminster Fuller, has gained new relevance as the Earth warms.

“We started thinking about how our museum can respond to climate change,” Abeer Saha, the curator who oversaw the dome’s reconstruction, said. “Geodesic domes popped out as a way that the past can offer a solution for our housing crisis, in a way that hasn’t really been given enough attention.”

Domes are just one example of the innovation underway. Houses made from steel and concrete can be more resilient to heat, wildfire and storms. Even traditional wood-framed homes can be constructed in ways that greatly reduce the odds of severe damage from hurricanes or flooding.

But the costs of added resiliency can be about 10 percent higher than conventional construction. That premium, which often pays for itself through reduced repair costs after a disaster, nonetheless poses a problem: Most home buyers don’t know enough about construction to demand tougher standards. Builders, in turn, are reluctant to add resilience, for fear that consumers won’t be willing to pay extra for features they don’t understand.

One way to bridge that gap would be to tighten building codes, which are set at the state and local level. But most places don’t use the latest code, if they have any mandatory building standards at all.

Some architects and designers are responding on their own to growing concerns about disasters.

On a piece of land that juts out in the Wareham River, near Cape Cod, Mass., Dana Levy is watching his new fortress of a house go up. The structure will be built with insulated concrete forms, or ICF, creating walls that can withstand high winds and flying debris, and also maintain stable temperatures if the power goes out — which is unlikely to happen, thanks to the solar panels, backup batteries and emergency generator. The roof, windows, and doors will be hurricane-resistant.

The whole point, according to Mr. Levy, a 60-year-old retiree who worked in renewable energy, is to ensure he and his wife won’t have to leave the next time a big storm hits.

“There’s going to be a lot of people spilling out into the street seeking sparse government resources,” Mr. Levy said. His goal is to ride out the storm, “and in fact invite my neighbors over.”

Mr. Levy’s new home was designed by Illya Azaroff, a New York architect who specializes in resilient designs, with projects in Hawaii, Florida and the Bahamas. Mr. Azaroff said using that type of concrete frame adds 10 to 12 percent to the cost of a home. To offset that extra cost, some of his clients, including Mr. Levy, opt to make their new home smaller than planned — sacrificing an extra bedroom, say, for a greater chance of surviving a disaster.

Building with steel

Where wildfire risk is great, some architects are turning to steel. In Boulder, Colo., Renée del Gaudio designed a house that uses a steel structure and siding for what she calls an ignition-resistant shell. The decks are made from ironwood, a fire-resistant lumber. Beneath the decks and surrounding the house is a weed barrier topped by crushed rock, to prevent the growth of plants that could fuel a fire. A 2,500-gallon cistern could supply water for hoses in case a fire gets too close.

Those features increased the construction costs as much as 10 percent, according to Ms. del Gaudio. That premium could be cut in half by using cheaper materials, like stucco, which would provide a similar degree of protection, she said.

Ms. del Gaudio had reason to use the best materials. She designed the house for her father.

But perhaps no type of resilient home design inspires devotion quite like geodesic domes. In 2005, Hurricane Rita devastated Pecan Island, a small community in southwest Louisiana, destroying most of the area’s few hundred houses.

Joel Veazey’s 2,300-square-foot dome was not one of them. He only lost a few shingles.

“People came to my house and apologized to me and said: ‘We made fun of you because of the way your house looks. We should never have done that. This place is still here, when our homes are gone,’” Mr. Veazey, a retired oil worker, said.

Dr. Max Bégué lost his house near New Orleans to Hurricane Katrina. In 2008, he built and moved into a dome on the same property, which has survived every storm since, including Hurricane Ida.

Two features give domes their ability to withstand wind. First, the domes are composed of many small triangles, which can carry more load than other shapes. Second, the shape of the dome channels wind around it, depriving that wind of a flat surface to exert force on.

“It doesn’t blink in the wind,” Dr. Bégué, a racehorse veterinarian, said. “It sways a little bit — more than I want it to. But I think that’s part of its strength.”

‘Looking for something different’

Mr. Veazey and Dr. Bégué got their homes from Natural Spaces Domes, a Minnesota company that has seen demand jump the past two years, according to Dennis Odin Johnson, who owns the company with his wife Tessa Hill. He said he expected to sell 30 or 40 domes this year, up from 20 last year, and has had to double his staff.

The typical dome is about 10 to 20 percent less than expensive to build than a standard wood-frame house, Mr. Johnson said, with total construction costs in the range of $350,000 to $450,000 in rural areas, and about 50 percent higher in and around cities.

Most customers aren’t particularly wealthy, Mr. Johnson said, but have two things in common: an awareness of climate threats, and an adventurous streak.

“They want something that’s going to last,” he said. “But they are looking for something different.”

One of Mr. Johnson’s newer clients is Katelyn Horowitz, a 34-year-old accounting consultant who is building a dome in Como, Colo. She said she was drawn by the ability to heat and cool the dome’s interior more efficiently than other structures, and the fact that they require less material than traditional homes.

“I like quirky,” Ms. Horowitz said, “but I love sustainable.”