See full article for full details, but here’s the Apple bit that caught my eye:

Back to that rain chance that your iPhone is teasing you with. It’s all a dirty lie. Aside from a less than 20 percent chance of a stray shower, there’s really not much to write home about in terms of rain chances. To put that chance into perspective, a number of meteorologists don’t even mention rain chances of less than 20 percent.

What’s causing the error? It’s honestly hard to say with any sort of certainty without working on Apple’s app development team. Weather apps that come preloaded onto smart phones have a notorious reputation for missing the mark when it comes to a forecast. A lot of times, the data that goes into these apps are raw and unfiltered. As anyone who works with data for a living can attest, raw and unfiltered data can be a land mine of trouble. Many of the most utilized weather apps, such as the stock iPhone app, are rife with real-world examples of why you should be getting your forecast from a trusted source. A human meteorologist remains the best source for accurate and reliable weather information.