The theme of this summer seems to be thunderstorms, bringing to my attention the fact that I had never considered what a good thunderstorm outfit would be. The clothing has to be breezy, as it'll be hot and muggy. It can't be too voluminous, as more wet material equals more sogginess and slower walking home. It has to be waterproof, and yet not made of something that would stick to you (since it'll be hot and muggy). It has to be a colour that won't stain from running makeup/sweat/colour from bag or other layers, a colour that makes you visible to cars when daytime suddenly turns dark, and a colour that doesn't make you look like you're in a wet t-shirt contest. It can't have any pockets that would contain disintegratable things. The shoes can't be flip flops in a serious downpour, they can't be something that will get wrecked from walking through river-like conditions, and they can't involve socks. The bag has to be waterproof, completely sealable in the event you have an electronics or a book you actually want to read/keep, and able to open immediately to get your keys out.
In other words: stay where you are and wait it out, always wear a Chromat suit (see video below for details), (and/)or take off your clothes.