You could also do 4 afghans (one for each season) and each afghan can have 3 columns (one for high temps, one for low temps and one for the weather. However, you may find that would be too busy depending upon your climate/city you are representing.
Alternatively, you could do granny squares and each square would represent the high, low and weather for each day and still do the 4 afghans to represent the seasons so it is not super large.
Let us know what you decide!
Thank you for the suggestions, Dmack. I'm still trying to figure out what I'll do, but I'm starting to warm to the idea of squares because I'm thinking of how the days are represented in blocks on a calendar. I've been sick with a sinus/inner ear infection since New Year's so for some reason I'm having a hard time thinking these days. I don't know if I do blocks, how big to make them or how many to do on a row. I'll let you know what I figure out. Thanks again!