I usually just want to know if it's going to warm up in the afternoon so I have a couple apps that are really simple and one that's just pretty. But if bad weather is coming in I go to Weather Underground. It's a good resource for the possibility of the earth killing you due to pressure differentials in the atmosphere or whatever
Maybe it's different where you are (some weather systems are more complex than others) but in Seattle any prediction beyond four days is science fiction. LA you could take it with a grain of salt out to six. Ten? That's some Nostradomus shit.