Current temp is the key one, which can vary widely throughout the day, is hard to tell by looking out the window and has the most impact on what you put on before you head out the door :)
Which would be great if it were something resembling the current temp but on all the weather apps I've seen the best you'll get is a weather forecaster's prediction (nothing actual) and the best accuracy is three hours.
Maybe that's just the UK and the US is getting something more accurate but I'm guessing not.
My Android phone's weather widget gives me the current temp, the daily high and low, and a general icon (sun, snow, freezing rain). Here in Massachusetts, it's accurate enough to be useful.
The spatial resolution on the weather data is pretty good; it distinguishes between my town and the next one over, and gives separate forecasts. The forecast is always a little different at home than at work (about 30 miles), but not too bad. Maybe it'd be a problem if I lived in the Bay Area, where the punchline of the "don't like the weather?" joke is not "wait 5 minutes" but "move 5 feet".
all i care about (in chicago) is whether it's going to rain or snow. the temperature or cloud cover don't really matter to me as much. http://goingtorain.com/
