It is colder than Antarctica today in much of the upper Midwest, and the record-breaking cold temperatures are grinding on the operations of e-retailers and shipping carriers, with the ripple effect expected to be felt for at least the next several days.

On Tuesday evening, UPS was forced to close its Rockford, Illinois, air hub due to weather conditions–the temperature dipped to 15 below zero there overnight–and reroute normally scheduled flights due in Rockford to its Worldport hub in Louisville, Kentucky, says UPS spokesman Matt O’Connor. The Louisville hub, where today the wind chill is 20 below zero, is working to accommodate the added flights and package volume and is also experiencing some service disruptions that will lead to delays.

“We are working around the weather,” O’Connor says. “We are operating as business as usual, the exception being in the areas where the polar vortex is making itself known.” That includes some localized closures of facilities in Iowa, Minnesota and Michigan, which means UPS will not make any pickups or deliveries in the affected areas today. FedEx, in a statement to Internet Retailer, says some operations and service may be affected in local areas, but it did not show any specific weather-related service issues on its service alerts page.

The United States Postal Service on Wednesday morning announced it was suspending deliveries in hundreds of ZIP codes due to the extreme cold. Areas not being serviced Wednesday include Chicago, Detroit, Cleveland, Cincinnati and Columbus, Ohio, as well as parts of Indiana, Iowa, Minnesota, Wisconsin, Nebraska, North Dakota and South Dakota. The USPS also will not be picking up commercial packages in some of the affected areas, including Minnesota, western Wisconsin, Iowa and western Illinois. The service suspension may extend into tomorrow, Jan. 31, as well, depending on conditions.

Brownells.com,  No. 165 in the Internet Retailer Top 1000, ships online orders from its facility in Grinnell, Iowa. Ryan Repp, director of content for the seller of firearm accessories and gunsmithing tools, said Wednesday morning it hadn’t experienced any weather-related shipping delays to date, but that they were “certainly not out of the realm of possibility” due to the just-announced service suspension by the USPS. Still, he’s confident the impact won’t be too hard. “Our delivery partners will be able to accommodate getting all current and day-behind orders out tomorrow, so the impact to customers should be minimal. We find our delivery partners are very helpful in finding solutions during unforeseen events.” Brownells.com emailed all customers whose orders will be impacted by the delay to alert them to this, Repp says.

Other online retailers in the region are alerting customers that orders may be delayed. Illinois-based e-retailers Grunt Style and North Shore Care Supply, No. 839 in the Top 1000, are alerting visitors to their homepages that orders may ship later than usual or be delivered later. Adam Greenberg, owner of North Shore Care Supply, says FedEx Ground pickup was cancelled today, but FedEx Express did pick up. “Traffic has been down about 20% yesterday and today on the site, but we’ve remained open for business ready to help customers,” Greenberg says.

Amazon.com Inc., meanwhile, closed several of its delivery stations in the Chicago area on Wednesday, citing weather conditions. Amazon buildings were also closed in and around Indianapolis, Milwaukee, Minneapolis and in Michigan. At checkout, Amazon customers may see a delayed promised delivery date. “The safety of our associates and delivery partners is our top priority, and we have temporarily closed buildings in areas affected by the freezing temperatures,” an Amazon spokesman says. “When one of our facilities or carriers is no longer able to operate safely, we work across our entire supply chain to minimize the impact to customers as much as possible.”

But at Madison, Wisconsin-based RockAuto.com (No. 199), general manager Jim Taylor says it is mostly business as usual. Employees made it into work, but some suppliers who drop ship orders on RockAuto.com’s behalf were closed. RockAuto.com added notices to its site as soon as it learned of these closures, and staff is reaching out to customers who ordered before those notices posted directly to alert them to potential delays.

At Abt Electronics Inc., No. 667, Chicago-area delivery and service staff were told to stay home Wednesday and Thursday, says Bryan Benavides, director of digital marketing. The consumer electronics retailer has a large retail store in the Chicago suburbs, and that is feeling the greater weather effect. “We are encouraging people to stay home and be safe, ” he says. “Internally, we are working with a skeleton staff of roughly 15% of our 1,500 employees.”

The silver lining is online orders at Abt.com are up about 10% for the day. Abt ships with UPS and Benavides says its UPS service has not been affected.

Rick Bentson, director of operations at AutoAccessoriesGarage.com, based in suburban Chicago and No. 802 in the Top 1000, says the e-retailer may get a sales bump out of the poor forecast. “We may actually make more money than usual today, because there are more people staying home from their jobs and many of them may be going online to shop,” he says. That said, AutoAccessoriesGarage.com sells winter essentials, like car battery boosters and wiper blades, that may give the e-retailer more attention than usual. The e-retailer also ships from multiple locations across the U.S., so Bentson expects any impact on deliveries to be negligible.

In Fort Wayne, Indiana, where Sweetwater Sound is based and where the high temperature on Wednesday is seven below zero, more employees made it into work than the company anticipated—a good thing, says Jeris Noye, senior vice president of logistics. Orders placed on Sweetwater.com are getting picked within a couple of hours, which is normal. Noye says the company received alerts from UPS and FedEx that there may be some delays, but “as usual both are working to avoid them and continue to be good partners.” Sweetwater is No. 83 in the Top 1000.

Dealing with frigid weather is par for the course for a lot of Midwesterners. Ron Weber, president of Plymouth, Minnesota-based iBuyOfficeSupply.com (No. 821), says the company’s office phones weren’t working this morning, and UPS and USPS wouldn’t be picking up or delivering today. “It happens and we deal with it,” he says. “We don’t expect to get through the winter without something like this so it is not a surprise to us.”

At RockAuto.com, Taylor notes, “Cold weather, in winter, in Wisconsin, is not unprecedented.”

This story will be updated.

Jessica Young, Bill Briggs and April Berthene contributed to this story.