The streets of Boston were nearly empty ahead of a massive winter storm on Thursday. (Spencer Platt/Getty Images)

When a Bostonian complains that it’s “wicked cold” outside, you know Mother Nature is not messing around.

Temperatures haven’t climbed to above freezing in that part of the Northeast since Christmas morning, and with a renewed blast of Arctic air en route, there’s no relief in sight. Boston has suffered a week-long “deep freeze,” tying the record set in 1918 for the longest stretch of days at or below 20 degrees Fahrenheit. That streak ended just before the “bomb cyclone” struck, but the cold was back in full force Friday morning.

It’s not just Boston that’s been a virtual Popsicle. Records were smashed across the Northeast. Temperatures in North Stratford, N.H., fell to 40 degrees below zero a week ago. What is minus-40 like? If you’ve seen the videos of freezing soap bubbles or boiling water turning into snow, you have an idea of how extreme it is. Many schools canceled or delayed classes to limit exposure to the dangerous cold.

The winds have been fierce over the past week, too. At the summit of Mount Washington, in New Hampshire’s White Mountains, the biting cold combined with howling gusts to yield a wind chill of minus-81. Fortunately, winds were much calmer at ground level, but there’s no other way to slice it: This cold shot is one for the record books.

Despite the chill, Boston has yet to register a below-zero reading this season. The official Weather Service sensor is at Logan Airport, which sits atop a peninsula surrounded by the (relatively warm) ocean on three sides. This makes it difficult for Logan to drop below zero, though it’s happened a few times in the past. On Valentine’s Day 2016, the airport thermometer fell to minus-9 in what proved to be its coldest overnight low since 1957. The record was forecast well in advance, but cracked train rails and cold vehicle engines plagued morning commuters.

Residents of Winthrop, Mass., a suburban community outside of Boston, began to clear the streets of snow on Jan. 5 after a powerful winter storm inundated the town with icy seawater. (Melissa Macaya/The Washington Post)

While the cold was a headache for many, it brought about a rare and stunning display of sea smoke, which occurs when very cold, dry air passes over relatively warm water. The moisture from the water saturates the air quickly and gives rise to tendrils of fog resembling wafting from the surface of the ocean. If the wind is just right, small eddies and whirls (sometimes called steam devils) can spin up. On extreme occasions, a few of these vortices may stretch all the way up to the clouds above, creating the elusive winter waterspout. Early risers may catch a few of these off the Maine, New Hampshire and Massachusetts coastlines over the weekend. The phenomenon can’t be ruled out over Lake Champlain, as well.

Now that this week’s big storm has departed, a flash freeze is possible in southeastern Massachusetts. That means areas that initially saw rain as the system swept in milder air will quickly drop below freezing — turning wet roadways into a perilous sheet of ice.

In Boston, the high will only be around 7 degrees on Saturday. If it’s any colder than that, it will be a record for the coldest high temperature for the date. And, despite the airport’s proximity to the relatively warm ocean water, even its temperature is likely to plummet to around minus-5 Sunday morning.