Turn climate data into a knitted accessory and a crafty conversation starter

Not your grandma’s knitting project.
Temperature scarf hanging from a tree
Who said data can't be fashionable? Sandra Gutierrez G.

As seasons change, you may wonder how your local climate has evolved over time. You also might think pulling up a sheet of weather data is the only way to know for sure whether spring appeared out of nowhere or winter really was colder and longer than it was five years ago. You’d be wrong—you can knit or crochet a fashionable garment instead.

OK, maybe you wouldn’t be completely wrong, as you will have to look at some numbers to set up this project, but we firmly believe a colorful accessory is a far more interesting way to visualize data than a utilitarian spreadsheet. No matter what you make, you can link it to your hometown for some added emotional attachment, or make one item with new temperature data and another with older numbers to see how climate change is affecting your town or city.

Basically, you’ll knit 365 rows, one for each day of the year, and the color of yarn you use for each one will depend on the average temperature that day. And after a year of crafting, you’ll have more than a cozy garment to keep you warm through the winter—you’ll have a stylish conversation piece to discuss with anyone who wants to know what the pattern means.

We’ll discuss planning more than process here because this project can truly be anything you want it to be. You can go big and make a toasty blanket to hibernate under, or simply make a basic scarf. You can customize colors as well—a classic rainbow scheme will ask for cold hues for winter, and warmer ones for summer, but randomly assigning your favorite tones to the temperature scale will give your project a personal touch. 

Before you knit, plan

Making a scientifically accurate temperature scarf or blanket will require some thinking. Careful preparation will also prevent you from having to get more yarn (and maybe not finding it), or ending up with an oversized project—be that a scarf longer than a reticulated python or a blanket big enough to cover your car. 

Get a good data source

If you’re highly disciplined and plan on adding to your project daily for an entire year, you can choose your colors by checking your favorite weather app and calculating each day’s average temperature. 

But let’s be honest: it’s incredibly hard to maintain that level of consistency for 12 months. That’s why your best bet is to find a platform that displays official weather data from the National Oceanic and Atmospheric Administration. There are many, but some are easier to use than others. 

We got our numbers from the National Weather Service Forecast Office’s website, which has daily weather data going back to 1948 and allows you to easily copy and paste numbers without disastrous formatting. Find your general location on that map, click on it, go to Climate and Past Weather, and select the NOWData tab on the far right. For a more specific location, scroll down the menu under Location and find the weather station closest to you. Under Product, select the bubble next to Daily data for a month, and then use the calendar under Options to choose a month and a year. Click Go, and the system will show you a table with different columns of information. The one you’ll need for your project is the one headlined Average (fourth from the left).

Determine how many colors you’ll use

This sounds like something to decide at the yarn store, but it’s crucial to think about it beforehand. The more hues you have, the more accurate your weather record will be. But more colors will make your project more expensive, as you’ll need to buy balls of different yarns.

[Related: How to knit your own Bernie mittens]

Going for nine or 10 colors will give your project compelling visual variety. Don’t use fewer than five, though—you’ll end up with big chunks of the same color and won’t be able to show how temperature ranges within seasons.  Don’t buy your yarn yet, though.

Sort your data

Now that you have your aesthetic, it’s time to create temperature brackets. This will help you avoid assigning (or spending money on) colors you’ll barely use.

For example, if you were using New York City’s 2020 temperature data, you’d see a minimum of 11 and a maximum of 97 degrees Fahrenheit. You’d divide that 86-degree-range by the number of colors you chose to come up with the size and location of each bracket. A smaller range also means smaller brackets, which will allow you to account for even more changes in weather. 

Once you’ve figured that out, copying and pasting your data into a spreadsheet will be the most efficient way to visualize it—you’ll be working with a single file, and you’ll be able to delete the columns you don’t need (most of them). 

The green line in the middle is that last cold day in April that unexpectedly ruins your outdoor plans. Sandra Gutierrez G.

[Related: Spies once used knitting to send coded messages—and so can you]

Using a spreadsheet also allows you to automatically assign colors to each temperature bracket by using conditional formatting. This feature (available within tools like Microsoft Excel and Google Sheets), will automatically paint a cell a particular color depending on its value, so you’ll know what color corresponds to each day’s average temperature. 

In Google Sheets, select the column with the average daily temperatures, then click on the paint bucket. In the emerging dialog box, scroll down to Conditional Formatting and click Add another rule. Under Format cells if…, open the drop-down menu and choose Is between. You’ll see two new fields where you’ll need to determine the low and high bounds of the first temperature bracket. If your colors will vary every 10 degrees, for example, you might start with a bracket that goes from zero to 10.

Under formatting style, click the paint bucket and choose the color you want to assign to that bracket. If you can’t find the exact color you want among the swatches, click on Custom and either find it manually or enter its hex code

Finally, click Done to save the rule, and repeat the process for every color you want to use. 

If this sounds like way more work than you have time for, we’ve got a gift for you: a Google Sheet filled with tabs featuring New York City (where Popular Science is based) weather data from 2020 and 2021 up to the day of writing. To use the spreadsheet, log into your Google account, open the link, make a copy of it (File > Make a copy > OK) and save it to your Google Drive. We’ve also added an empty tab so you can paste the average temperatures from your hometown. When you paste the data in, the cells will automatically change to the corresponding color in the key, which you’ll also be able to change.

If you just want to work on a month-by-month basis, you can download a new file every 30 days. Once you have a table on the NOWData tool, save it to your hard drive by clicking on Print and choosing Save as a PDF from the drop-down menu next to Destination.

Buy your yarn

Now it’s time to get your supplies. Your first instinct may be to get one ball of yarn for each color you’re using, but that’s the wrong approach. There are some colors you’ll be using more than others. 

Take a look at your data to find what range of temperature is more common throughout the year in your location, and buy at least two balls of yarn of the color corresponding to that range. If you’re using current data, you can have a good idea of what those ranges are by peeking into last year’s data. 

Although it may be inevitable, you want to avoid having to go back to the store to get more yarn. Dyes may vary depending on what batch they belong to, so you may have a hard time finding the exact same color again five months down the line.

Swatch, swatch, and then swatch again

You can design this project however you please: you can knit or crochet it, and choose the stitches you use, the colors, and even the shape it takes. Want to do a blanket? Go ahead. Don’t want to deal with the commitment? Make a scarf. Are you an overachiever? Turn it into a rug or a tapestry. 

There’s just one thing that unequivocally will not change—your project will have 365 rows. This may not sound that important now, but you may find yourself with a 7-foot-long knit with two more months to go, depending on the yarn you choose. That’s less of a throw blanket and more like a piece of Paul Bunyan’s winter wardrobe. Go too small and you could get a blanket that barely covers your feet.

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The best way to prevent this is by knitting a swatch that’s 20 stitches wide and 20 rows long with a yarn that’s similar in thickness to the one you’re planning to use. When you’re done, measure its length and multiply that number by 18.25 (365 divided by 20) to get the final length of your project. You can adjust the number of stitches in your project’s width to make it proportionate, or you may opt for a thinner yarn to decrease it. If you do the latter, you’ll have to knit a new swatch to get precise final measurements.

To be super sure your dimensions are correct, get one ball of the yarn you plan to use for your project, and swatch and measure again. Once you’re satisfied, you may buy the rest of your supplies without any regrets. 

Knit away 

That’s it—those are the instructions.  

From here on out, you are free to determine all the details concerning your project, and you may even want to change things up to make it more interesting.

Add more data

Keep track of snowy and rainy days by marking them. If you’re using knitting needles, you can try a jacquard pattern or, if you’re crocheting, you can use a tapestry technique to alternate colors. You can use white for snowy days and light-blue yarn for when it rains. 

Do a comparison

We’ve touched on this briefly already, but using two datasets will make things more informative, if slightly more complicated. You can pick weather records from the same location in two different years, and knit them side by side to see how they’ve changed over time. You can also pick two places in the same year (maybe the town you grew up in, and your current location), and see how different they are. 

Stitch labels on it

Make sure you know what year the data reflected in your project comes from. That way, if you turn this project into a tradition, it’ll be easier to compare how climate change has affected a particular area. Once you finish, cut a square of muslin and write the corresponding year and location on it with a permanent ink marker, then stitch it onto your project. If you want, you can use the same technique to make the textile equivalent of a sticky note to mark important days, such as your birthday, or weather events, such as storms or hurricanes.