Temperature mode.

[patfla]

It'd be nice when the temperature overlay is activated to, for example:

1. turn off all animations.
2. display numerical temperature values at reasonably spaced locations (and have that change with zoom).
3. mouseover those numbers and have some textual info about the location pop up.

I've cloned the code and am looking through it to see how it works.

Not that it's surprising but inspecting the current temperatures I find that the coldest temperatures (currently winter in the northern hemisphere) are all, pretty much, located over continents. There are a number of interesting things that can be learned from the current temperature overlay.