Short answer: multiply the days in each temperature band by the yards one row takes. With 12 yards per row, the 365 days of Chicago's 2025 come to 4,380 yards in total, but the split is very uneven: from 24 yards for the rarest color to 768 for the most common.
Measure one row first
Everything depends on yards per row, and that depends on your stitch, hook or needles, yarn and blanket width. Work one row at the width you want, unravel it and measure the yarn, then add a little for joins. We use 12 yards per row here only as an example. Do not copy our number: measure your own.
A real year: Chicago, 2025
These are the daily high temperatures from NOAA's National Centers for Environmental Information for station USW00094846 in Chicago, sorted into the classic 10 °F bands. One row per day, 12 yards per row, skeins of 200 yards:
| Daily high | Days (rows) | Yards | Skeins |
|---|---|---|---|
| 0 to 9 °F | 2 | 24 | 1 |
| 10 to 19 °F | 8 | 96 | 1 |
| 20 to 29 °F | 25 | 300 | 2 |
| 30 to 39 °F | 35 | 420 | 3 |
| 40 to 49 °F | 44 | 528 | 3 |
| 50 to 59 °F | 57 | 684 | 4 |
| 60 to 69 °F | 43 | 516 | 3 |
| 70 to 79 °F | 60 | 720 | 4 |
| 80 to 89 °F | 64 | 768 | 4 |
| 90 to 99 °F | 27 | 324 | 2 |
The most common band, 80 to 89 °F, needs 32 times as much yarn as the rarest, 0 to 9 °F. Buying the same amount of every color would leave you short of some and with leftovers of others. Added up by color, this example needs 27 skeins, against 22 if all the yarn could come from one color, because each color rounds up separately.
The catch if you start in January
You do not know next year's weather when you buy your yarn. These were Chicago's monthly highs in 2025:
| Month | Average high | Coldest high | Warmest high |
|---|---|---|---|
| Jan | 30 °F | 2 | 50 |
| Feb | 34 °F | 9 | 57 |
| Mar | 54 °F | 34 | 79 |
| Apr | 60 °F | 43 | 84 |
| May | 68 °F | 52 | 94 |
| Jun | 84 °F | 70 | 95 |
| Jul | 86 °F | 72 | 95 |
| Aug | 82 °F | 70 | 95 |
| Sep | 79 °F | 66 | 89 |
| Oct | 66 °F | 50 | 89 |
| Nov | 49 °F | 31 | 71 |
| Dec | 34 °F | 10 | 56 |
Use last year's numbers for your city as a shopping guide, and buy a little more of the colors around your typical temperatures. If you buy in stages, buy from the same dye lot where you can. Or make a blanket of a year that has already ended, where every number is known.
Get your own numbers
Our temperature blanket planner does this for your city. Type the city, pick a year, enter your yards per row and skein size, and it fetches the daily temperatures from NOAA and gives you the days, yards and skeins per color, plus a printable tracker. For crochet rows or granny squares, see the crochet temperature blanket page. NOAA's data covers mainly the United States, and stations outside it have gaps.