Entire Planet
This shows a clear trend of temperatures corresponding with latitude, with a peak just a bit north of the equator.
Although there are other regression algorithms which would likely fit better, for this analysis, only linear regression is considered.
North Only
As shown in this chart, there is a clear correlation between latitude and temperature.
In order to reduce fluctuations between night and day (since the query would have run at a single time, but checked temperatures globally), only daily maximum temperatures are used.
South Only
As seen in the northern hemisphere, there is a strong correlation between latitude and temperature.
Note that there are far fewer points to choose from. Although the randomly-seeded coordinates would be evenly distributed, any time there is a repeated city name (found via closest coordinate), the new location is discarded from the set. There is much less landmass south of the equator than north, so this is working as intended.