Okay, so you're thinking that it's an overcast or drizzly day, and you're going to spend the day inside working on your photos in Photoshop. That's not the worst idea in the world, but you'll miss some great shooting opportunities, like:
Right after a rain, while it's still cloudy and dark, is the perfect time to shoot foliage, forests (the green leaves look more saturated and alive, even leaves on the ground look good, plus the water droplets on the leaves and flowers add interest), mossy rivers, and waterfalls (you can use slower shutter speeds while the sun is buried behind the overcast rain clouds).
If it's storming, there's a good chance that right after the rain stops, and the clouds break, and the sun peeks through, there's a very dramatic shot coming. It may only last a couple of minutes, and it will either start storming again or clear up and just get really sunny (an outdoor photographer's enemy), so be ready for those few magical moments between storms. They're worth waiting for.
Before the storm "lets loose," you can get some really amazing skies, with angry clouds and sometimes colorful light or strong light beams. Most people miss these shots, so be ready (just don't shoot in the rain, to protect you and your gear).
