Global Coolness
Kevin Wald
The numbers shown in the graphs are not temperatures, but angles; specifically, angles counterclockwise from due north. This is hinted at in the flavortext; Route 2A is at about 25 degrees counterclockwise from north as it passes by the 77 Mass Ave steps at MIT, and about 10 degrees clockwise from north as it passes Johnston Gate at Harvard (those being the two sites depicted in the photographs).
Thus, each "day" shown in each graph has two angles associated with it, one from the gray line and one from the crimson line. From the two observation points, if you draw rays at the corresponding angles (gray from MIT, crimson from Harvard), they will intersect at a unique point. Thus, for each graph, a set of points is traced out on the map. The result is as follows:
That is, reading northward, "1.5°N of" followed by a centered dot. If you go 1.5 degrees of latitude north of the point on the map marked by the dot, you are near the town center of Madison, NH. Putting this location in the format used for all cities mentioned in the flavortext, you get the answer: MADISON, NEW HAMPSHIRE.