Every evening, she knits two rows onto her latest handiwork, selecting Thistle-colored yarn if it's 14 degrees or below, Almanac if it's between 15 and 29, or Faded Quilt for 30 to 44.

At the end of the year, if all goes well, she'll have a 6-foot-long temperature scarf displaying 2019's weather through its color pattern.

Matthews is one of roughly 200 crafters participating in a knit-along sponsored by the Yarnery in St. Paul. Dubbed Weather or Knot (yarn shops can't resist a good pun), the project is a spinoff of what's become crafter catnip around the world: the temperature blanket, a multicolored throw visualizing a year's worth of weather.

Row by row and share by share, the photogenic handicrafts have caused heat waves on social media among fiber-art enthusiasts.

Temperature-sensitive knitters say the daily ritual helps them pay attention to the weather and connect with crafters in other climes. While it's part of a broader "data art" movement that helps make abstract information more accessible, there's also an aspect of "craftivism," in which crafters convey political messages in homespun media. From the AIDS Memorial Quilt of the 1980s to the hot pink pussy hats from the 2017 Women's March, the concept is seen as a "gentle" form of protest.

There are endless riffs on the temperature blanket, but the fundamentals are the same: It's a yearlong project that displays each day's weather though yarn colors that correspond to a temperature key. The typical color palette reflects the rainbow hues of weather maps — from freezing purples to scorching reds — but any suite of hues may be used.

Though blankets are the most popular form of temperature textile, there are plenty of scarves and tapestries. While many are knit, they may also be crocheted or woven.

Weather or Knot was created by Scott Rohr, co-owner of the Yarnery. He was inspired by a group in Washington state that created a series of "tempestries," scarf-size wall hangings showing annual temperature data from 1950s to today. The pattern Rohr created reflects weather (time-specific atmospheric conditions) through its color selection and climate (average conditions) through the stitch.

Rohr's design specifies that knitters in the Twin Cities area use seven colors to represent temperature increments of 15 degrees, and adjusts the scale for other climates. Each day, the knitter creates two rows in the color representing the day's high temperature.

The stitch pattern is based on whether the temperature was above or below the average high. As a proponent of American-produced wool, an industry that's very sensitive to climate change, Rohr said it was important to include this aspect in his design.

Matthews bought a Weather or Knot kit for herself and a friend in Seattle who is undergoing cancer treatment because she hoped it would be a forward-looking project that might add variety to her friend's day without being too taxing. She recruited another Seattle friend to join the knit-along, too, and the three periodically compare notes and share photos.

"I feel more in touch with both friends because of this project," Matthews said.

Creating a "virtual community" is part of the project, said Rohr, and participants frequently share images on Instagram (hashtags #weatherorknot and #yarnery).

"Knitters are just big nerds and we like different projects and ideas," Rohr said.

Data as art

While they're only two months into the project, several local knitters said they were surprised by the variability of January's temperatures.

Early in the month, the highs were warm enough for knitters to incorporate the fourth color in the temperature key, representing 45-59 degrees. One #weatherorknot Instagrammer captioned an image of her progress "Week 2 in Minnesota, where all the women are strong, all the men are good looking, and (almost) all the temperatures are above average."

By late January, the mercury dropped so low that a few local knitters decided to add an eighth color to reflect the subzero temps not accounted for by the original pattern.

Temperature blankets are among the many ways yarn is being used to visualize data.

A couple of artists in Barcelona, Spain, popularized the idea of "neuro knitting," creating textiles that record the pattern of an individual's brain waves. A German commuter created a scarf that depicts the length of time her daily train was delayed — and sold it for $8,600 on eBay.

Such creations are part of a larger "data art" movement, in which everything from game scores and flight patterns to sleep habits and peak breakup seasons (based on Facebook status updates, of course) are depicted visually.

The idea is to create something of aesthetic interest out of numeric information. But the patterns that emerge also turn dry, abstract numbers into something more relatable, something that can evoke an emotional response.

"Physical data visualizations are becoming popular these days because they make the data tangible and tactile," David McCandless, a noted British data journalist and information designer, wrote in an e-mail. "They feel more real than an image on a screen or a smartphone. And they go beyond the classic, clichéd pie, bar and line charts, meaning people take more notice. It's the power of novelty."

A University of Georgia marine scientist experienced this firsthand when she crocheted a scarf that reflected how the global average temperature deviated from normal over the past 400 years. Though she and her peers regularly pore over graphs that show the planet is warming, seeing the scarf turn from purple ("normal") to increasingly darker shades of red made that fact more visceral and resonant.

Motivated by the mission

Like many crafting endeavors, one of the biggest challenges of a yearlong weather-knitting project is keeping up.

Carly Stipe, manager of the Darn Knit Anyway (again with the puns!) yarn shop in Stillwater, once started a similar project called a "sky scarf," where the knitter bases each day's yarn selection on the color out the window each morning.

But Stipe fell behind in tracking the daily progression of blues, creams and grays, and abandoned the scarf after a month. "That one disappeared into my UFOs," she admitted, using the knitter shorthand for unfinished projects.

"I thought I would do it with my cup of coffee every morning, but then, of course, kids, and pets, and life."

Fortunately, weather archives make temperature-based projects easier to catch up on. Though many Weather or Knot participants said the scarves' mission-driven aspect has inspired them to maintain the regimen, as they hope it will help raise greater awareness about climate change.

Without her project, Weather or Knot participant Danielle Fillmore may not have noticed that the January high temperatures of her Hope, Mich., hometown reflected twice as many days that were warmer than average than those below average.

"The more people who are interested in the environment, the better," she said.