Covid-19 cases are climbing in places like the upper Midwest, Southwest and parts of the Northeast, hindering the nation’s progress in ending a surge triggered by the highly contagious Delta variant of the coronavirus.

Nationally, the seven-day average of new cases appears to be edging back up after hovering just above 70,000 for several weeks, according to data from Johns Hopkins University, halting what had been a decline from the Delta-fueled peak that began in September. While the Southeast cools off from its summer surge, other regions are under pressure, including places where colder weather has brought people back indoors where the virus can more easily spread.

The stalled progress is an unwelcome turn as the Thanksgiving holiday nears, which will mean more people traveling and congregating indoors, as families gather to celebrate.

“Right now we find ourselves in a really truly alarming spike in cases,” Jan Malcolm, commissioner of the Minnesota Department of Health, said at a briefing last week.

Minnesota has recently averaged more than 3,500 new cases a day, according to Johns Hopkins, the state’s highest level since last April. After a brief summertime lull, when the state reported only about two new Covid-19 deaths a day, the seven-day average is about 24 a day. The state recently topped 9,000 deaths since the pandemic began, according to Johns Hopkins.

The latest surge has begun overwhelming some hospitals. Gov. Tim Walz set up two temporary sites staffed by National Guard members and federal nurses to relieve hospitals caring for Covid patients.

States widely report the bulk of Covid-19 hospitalizations remain among unvaccinated or partially vaccinated patients, even as some states show fully vaccinated people have become a rising share of the mix.

The virus is spreading in other cold-weather places like Michigan and New England, including Vermont. Cases also are heating up in some Southwestern states like Arizona, which has recently averaged more than 3,000 new cases a day.

“After nearly two years, I don’t blame anyone for feeling done with the Covid-19 pandemic,” Don Herrington, interim director of the Arizona Department of Health Services, wrote in a blog post last week. “The unfortunate truth, however, is the pandemic isn’t done with us.”

The problem is mainly the still-unvaccinated population in the U.S., and waning immunity among people who got vaccine shots early on and now should get boosters, said Eric Topol, director of the Scripps Research Translational Institute in La Jolla, Calif.

Roughly 59% of the whole U.S. population is fully vaccinated, according to the U.S. Centers for Disease Control and Prevention, meaning they have received two doses of an mRNA vaccine or the single-dose Johnson & Johnson shot. And about one-third of people aged 65 and up have had a booster shot, CDC data show.