Every time weather.app gets mentioned, there always seem to be cries for a dynamic icon which I really don't understand. Sure, we have one for the calendar which makes sense as people often need to quickly check the date. However, do people really have a frequent need to know what the current temperature/weather is where they are? I've not been outside today, but looking out of my window I could tell you what the temp is out there and get it right to within a few degrees, which is the same level of accuracy you get with weather.app (if you're lucky). In fact, my eyes probably get it right more often than the app anyway. Even if you're working away in a windowless environment, the temperature outside is not going to be much different than what it was when you got to work. And in that case, why do you need to know the temp anyway - what are you going to do different? If there's critical things you need to do due to changes in the temperature, I'd suggest you should be running an accurate monitoring system rather than relying on an iPhone app giving approximate local conditions.
This really isn't a dig at anyone, I'm really just at a loss to understand why people actually want this with such a passion (beyond the gimmick factor). The only real 'use' I can see it being put to is when you're in the garden with your wife and she says "phew, it's hot", you can glance at your iPhone and say "yes, it's xx degrees!". Someone help me see the need please!
There's also issues of practicality (as with having a dynamic clock.app icon which really would be a gimmick) - you've got to have icon images for every combination of conceivable temperature (in both celcius and fahrenheit) and weather (sun, rain, snow, cloud etc) - that's quite a few. At least calendar.app only needs 31.
However, now I've got all that off my chest, let me point out that the weather.app icon actually
is a dynamic icon - if you've got the weather set to appear in fahrenheit it shows 73 all the time, if you've got it set to celcius in shows 23.