There’s no arguing that Google’s self-driving car is a thrilling development worthy of enthusiastic discussion, but there are a number of reasons to rain on this parade – rain itself, for one thing. That’s because the autonomous automobile has yet to prove that it can drive through heavy rain, not to mention snow, parking garages and many other everyday driving scenarios. Despite the more than 700,000 miles Google’s self-driving cars have traversed so far, they still have many hurdles to overcome. While the cars can slow down or stop when traffic or obstacles are detected, they aren’t able to know if a new stoplight pops up overnight, according to the MIT Technology Review. The cars can detect and stop at unmapped stop signs, but a four-way stop may cause them to be overly slow and cautious.