My city is NYC. I had to graph the 12 months and figure out a the period, midline, amplitude, and horizontal shift.. then find a function for it. I'm really bad at all this. heres a link to a pic of the original graph with all the data as well. Original Graph | Flickr - Photo Sharing!
I got 22.5=Amplitude Pi/6=Period 54.5=midline and 11=horizontal shift.
the function i used was 22.5*sin(Pi/6x+11)+54.5 and i plugged it into excel for each average.. heres a pic of what it came out as.
Graph with functions | Flickr - Photo Sharing!

HELP ME!! i don't know if i did any of this right and I'm confused.

I'm also supposed to predict which days in 2012 that the average temp will be 62 and to show my work.. I don't know how to do that.