I have yet to find an app that's 100% accurate across the board, and I find Accuweather isn't the greatest for precipitation.
I rely on 3 apps: Accuweather Pro (not the G3's built-in app), TWN (The Weather Network - pretty much The Weather Channel but Canadian content), and WeatherBug. Between the 3 I can get a pretty decent idea of what it's going to be doing. Accuweather is pretty good with temps, not so much with wind and precipitation. TWN is good for wind, and much better then Accuweather for precipitation, WeatherBug is a nice overall app - it's nice to have a 3rd input to get a reading on the day's weather - it's also nice that I can set alerts for severe weather, not just for my home location, but any location I set.