I'm getting a slightly late start, but this is going to be a year long project as well: a temperature scarf. Each color represents a temperature range, and every day I will knit two rows in the color that shows the high temperature for that day. The ice gray is -16°C and below. The dark brown (which I inexplicably switched with red for the photo) is 35°C and above, and the remaining colors are 5° increments. It will be interesting to see how it turns out - I think the only thing I can really guarantee is that the dark brown and light gray will never be next to each other!
I'm also going to use this project to force myself to think in Celsius, since I know exactly this much: 0 =32, 20=68, and 100=212.