Taking photos in bad weather is something all photographers try to avoid. Aside from possible damage to your equipment and poor lighting conditions, it's just never really comfortable to be in and out of the rain trying to stay dry. But when you are traveling and have spent considerable funds to be wherever it is you are, then you need to make the most of the situation. So you are out in the rain and the light isn't perfect. What then?
The difference between a pro and an amateur is how you deal with adverse conditions. There are lots of opportunities if you look closely. In the early morning and towards dusk look for beautiful reflections off the wet ground. In a city environment, look for the headlights reflecting off the street. People with umbrellas moving about can make for some interesting images. In a more natural environments, look for a light fog after the rain. Opportunities abound, you just have to be willing to look for them. And always make sure you are dressed warmly and have taken precautions to protect your equipment.