Amid an autumnal heat wave sweeping much of the country, rare red flag warnings were issued for Chicago and western Oklahoma, while firefighters reported they had gained the upper hand on a wildfire that threatened homes in Colorado.

It may be late October, but the U.S. wildfire season has reignited across the country, with at least 11 active wildfires burning from California to New Jersey, officials said.

The National Weather Service issued a red flag warning for western, northwest and northern Oklahoma, where firefighters are battling multiple wildfires near the towns of Cushing, Chickasha, Cimmaron City, Wellston and Seiling. The fires led to the evacuation of some homes and destroyed “some” residences in Logan County, according to Logan County Emergency Management.

The largest active fire in Oklahoma is the Rush Fire, which has burned more than 12,000 acres in the Wichita Mountains National Wildlife Refuge, about 70 miles southwest of Oklahoma City. The fire, which broke out Thursday, was 48% contained as of Tuesday evening, officials said.

The NWS also issued an advisory for the Chicago area on Tuesday, saying in an alert: “Critical fire weather conditions are either occurring now or will occur shortly.” The temperature rose to 82 degrees in Chicago on Tuesday, setting a daily heat record .

Gusty winds and bone-dry conditions contributed to the spread of a grass fire that broke out south of Chicago on Tuesday, shutting down part of Interstate 74 due to the smoky conditions, officials said.

Peak fire danger is forecast for the southern Plains, including Oklahoma, Kansas and Texas, on Wednesday.

Dangerous fire conditions are also being seen in parts of New Mexico, where officials have issued a “state of preparedness” notice for residents of Bonito Lake in Lincoln County to prepare to evacuate in the event of the Blue Front Fire, which broke out Monday and had burned 270 acres by then. Things get worse on Tuesday.

According to the Colorado Fire Department, the Highland Lake Fire, which broke out around 4 p.m. Monday and burned 166 acres near the town of Divide, was 80% contained as of Wednesday afternoon. All evacuation orders have been lifted, Teller County Sheriff Jason Mikesell said at a news conference Wednesday.

“The reason this was so successful and the reason we are here 72 hours later and not seven days later is all the work that was done that first day, that first night,” Mikesell said.

The sheriff said investigators focused their investigation into the cause of the fire on a building that was destroyed by the flames. He said investigators believe the fire was “human-caused,” but it remains unclear whether the cause was accidental or criminal.

Mikesel said frontline firefighters faced winds of more than 50 mph and gusts of more than 60 mph Tuesday but were able to make significant progress in containing the fire.

Mikesel said about 150 firefighters were battling the blaze Wednesday.

The Teller County Board of Commissioners declared a local disaster.

No injuries were reported.

The sheriff’s office asked for and received help fighting the fire from several agencies in the area, Mikesell said.

The NWS has issued warnings for dangerous fire conditions in the Divide area.

Elsewhere, a red flag warning was issued this week in Massachusetts, where firefighters continue to battle a 400-acre brush fire near Salem. Firefighters are also battling another brush fire that broke out Sunday and burned at least 250 acres near Middleton, Massachusetts.

At least 11 large active fires in the United States have burned more than 1 million acres, according to the National Interagency Fire Center. At least 4,000 wildland firefighters were battling the fires, according to the center.

Wildfires also burned in Michigan, Wyoming, Utah, Oregon and New Jersey.

The increased risk of forest fires comes against the backdrop of record high temperatures across the country. On Monday, records for high temperatures were reached or even broken in dozens of cities, including Oklahoma City. Kansas City, Missouri; Wichita, Kansas; Minneapolis, Minnesota; Witchita Falls, Texas; and Austin, Texas.

In Minneapolis, temperatures rose to nearly 80 degrees on Monday.

The NWS also issued a rare advisory this week for New York City, which hasn’t had any measurable rain in about a month.

In New Jersey, Gov. Phil Murphy issued a draft watch advising businesses and residents to conserve water.

A wildfire that broke out last week in the drought-stricken area near Rockaway Township in Morris County, New Jersey, burned nearly 80 acres of land, officials said.

On Monday, the NWS issued a special weather statement in Philadelphia and New York City warning of an increased risk of wildfire spread.

The statement said: “Vegetation remains very dry and could potentially serve as fuel for fires. These conditions will encourage the spread of fires that ignite and could quickly become difficult to control.”