That depends, is it pouring buckets or just raining?
If just raining, just walk were you are going, maybe put a hat on.
If it's pouring, you run from "here" to "there", as long as it is a relatively short distance, (bldg to car).
I love watching and laughing at people (usually women) carrying and fighting with umbrellas when it's barely sprinkling. Unless you are in a photo shoot, your hair-do isn't that important. And if you are in a photo shoot, the stylist is going to fix your hair after every few shots anyway.