This is beautiful! I'm very happy. Thank you.
I just saw your edit. The formulas for celcius and fahrenheit are different.
Also, some minor things:
1. The f in feel like should be capital F.
2. There should be an s at the end of feel to read Feels. Thats more grammatically correct.
3. The L in like could be capital L.
4. The ` between high and low could be / because it looks better.
One more thing, in the main window, for the low/high of the 5 days, please change to high low and add + for the positive degrees. (mine said -4/3 and I thought it was -4/-3 but its really -4/+3 so change to make it +3/-4)
You know, if you really wanted to get fancy, you could get all the same information in the tooltip for today and use it for the 5 days, the only thing different is 5 different urls, but the same scripting.