My guess is that's accounted for in each city by the m and k values. Note that these values are essentially averaging the battery-temp-affecting behavior of everybody in a given location (as well as the local temperature variations as well) and mapping them to the "official" temperature (usually measured at the airport). That makes the whole exercise rather useless in my opinion: it doesn't provide more information than a weather report, just a vague redundancy. Significantly, they will never be able to isolate all the factors so that a single phone can tell you the local air temperature.

As Dylan famously said: "You don't need a weatherman to know which way the wind blows."[1]

[1] http://en.wikipedia.org/wiki/Subterranean_Homesick_Blues